S T 1 2 4 0 0 W SEAGATE NO MORE PRODUCED Native| Translation ------+-----+-----+----- Form 3.5"/HH Cylinders 2626| | | Capacity form/unform 2148/ 2537 MB Heads 19| | | Seek time / track 9.0/ 2.0 ms Sector/track | | | Controller SCSI2 SI/WI/FAST Precompensation Cache/Buffer 256 KB SEGMENTED Landing Zone Data transfer rate 4.000 MB/S int Bytes/Sector 512 20.000 MB/S ext SYNC Recording method RLL 1/7 operating | non-operating -------------+-------------- Supply voltage 5/12 V Temperature *C 5 50 | -40 70 Power: sleep W Humidity % 8 80 | 5 95 standby W Altitude km -0.305 3.048| -0.305 12.192 idle 9.0 W Shock g 10 | 60 seek W Rotation RPM 5411 read/write W Acoustic dBA spin-up W ECC Bit REED SOLOMON MTBF h 500000 Warranty Month 60 Lift/Lock/Park YES Certificates CSA,EN60950,FCC,UL1950,VDE ********************************************************************** L A Y O U T ********************************************************************** SEAGATE ST12400W/WD PRODUCT MANUAL 77767457 REV. C 17/3/95 +---------------------------------------------------------+ | |XX1 | |XXPower | |1-+ | || J5 ++LED || | ++ |+-+ | |+1+ | ||X|I/O | ||X| | ||X| | ||X|J1 | ||X| |+-+ ||X| || |J6 ||X| |+-1 8--------1 ||X| | +--------+J2 |+-+ +---------------------------------------------------------+ ********************************************************************** J U M P E R S ********************************************************************** SEAGATE ST12400W/WD PRODUCT MANUAL 77767457 REV. C 17/3/95 Jumper Setting ============== REAR VIEW +------ 5V | +---- GND (TOP) | | +-- GND 34 1 1 | | | + 12V +---------------------+ +-J5---+ +-------+ ----+|||||||||||||||||||||+--+::::::+-+O O O O+- +---------------------+ +------+ +-------+ 68pin I/O Cable |||||| Power SCSI ID = 0 (none) Connection |||||+----------- SCSI ID = 1 ||||+------------ SCSI ID = 2 |||+---------+--- SCSI ID = 4 or pin-6 ||| +--- REFIND+ ||+-------------- SCSI ID = 8 |+--------------- pin-10 GND +---------------- pin-11 +5V J5 SCSI ID ----------- +----------+-------------------------------+ | SCSI ID | Jumper Location | | | PINS | | | 7-8 | 5-6 | 3-4 | 1-2 | +----------+-------+-------+-------+-------+ | 0 | OPEN | OPEN | OPEN | OPEN | +----------+-------+-------+-------+-------+ | 1 | OPEN | OPEN | OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 2 | OPEN | OPEN | CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 3 | OPEN | OPEN | CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 4 | OPEN | CLOSED| OPEN | OPEN | +----------+-------+-------+-------+-------+ | 5 | OPEN | CLOSED| OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 6 | OPEN | CLOSED| CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 7 | OPEN | CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 8 | CLOSED| OPEN | OPEN | OPEN | +----------+-------+-------+-------+-------+ | 9 | CLOSED| OPEN | OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 10 | CLOSED| OPEN | CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 11 | CLOSED| OPEN | CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 12 | CLOSED| CLOSED| OPEN | OPEN | +----------+-------+-------+-------+-------+ | 13 | CLOSED| CLOSED| OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 14 | CLOSED| CLOSED| CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 15 | CLOSED| CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+-------+ RIGHT SIDE VIEW +-J1 TOP (HDA) |X+------------+--------+-----PWA--------------------Front of drive +-+ |12345678|J2 +--------+ +Terminator PWR -+||||||+- RESERVED +Terminator PWR --+||||+-- Start Delay (12 secs * ID) | Enable T-Res ---+||+--- Motor Start | Parity Enable ----++---- Write Protect | | Terminator Power-source Table ----------------------------- 1 2 1 2 1 2 +---- +---- +---- |X o |o X |o o |X o |o X |xxx +------ +------ +------- Drive Supplies Drive Supplies Bus Supplies Bus Own Drive (Position A) FRONT VIEW J6 TOP (HDA) +-----1+ -------PWA--------------------------------+::::::+--- ++ +------+ SCSI ID = 0 none ++LED pin-11 +5V --+||||+-- SCSI ID = 1 pin-10 GND ---+||+--- SCSI ID = 2 SCSI ID = 8 or -+--++--+- SCSI ID = 4 or pin-8 BUSY -+ +- pin-6 REFIND+ NOTE If these ID jumper are used, the ID jumpers J5 ARE NOT USED!!!!! J6 SCSI ID ----------- +----------+-------------------------------+ | SCSI ID | Jumper Location | | | PINS | | | 7-8 | 5-6 | 3-4 | 1-2 | +----------+-------+-------+-------+-------+ | 0 | OPEN | OPEN | OPEN | OPEN | +----------+-------+-------+-------+-------+ | 1 | OPEN | OPEN | OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 2 | OPEN | OPEN | CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 3 | OPEN | OPEN | CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 4 | OPEN | CLOSED| OPEN | OPEN | +----------+-------+-------+-------+-------+ | 5 | OPEN | CLOSED| OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 6 | OPEN | CLOSED| CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 7 | OPEN | CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 8 | CLOSED| OPEN | OPEN | OPEN | +----------+-------+-------+-------+-------+ | 9 | CLOSED| OPEN | OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 10 | CLOSED| OPEN | CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 11 | CLOSED| OPEN | CLOSED| CLOSED| +----------+-------+-------+-------+-------+ | 12 | CLOSED| CLOSED| OPEN | OPEN | +----------+-------+-------+-------+-------+ | 13 | CLOSED| CLOSED| OPEN | CLOSED| +----------+-------+-------+-------+-------+ | 14 | CLOSED| CLOSED| CLOSED| OPEN | +----------+-------+-------+-------+-------+ | 15 | CLOSED| CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+-------+ Drive ID/option select header ----------------------------- Both J1-auxiliary and J6 have pins for selecting drive ID and for connecting the synchronized spindle cable and the remote LED cable. Only one or the other should be used, although using both at the same time would not damage the drive. The notes ([1]-[9]) following the figures describe the functions of the various jumper positions on the three connectors J2, J1-auxiliary and J6. Sug-gested part number for the unusual J2 jumper is Molex 52747-0211 (Seagate P/N 77679052). Notes explaining the functions of the various jumpers on jumper header connectors J2, J1-auxiliary and J6 are given below in left to right order of jumper position. The term "default" means as standard OEM units are configured when shipped from factory. "Off" means no jumper is installed; "On" means a jumper is installed. "Off" or "On" underlined is factory default condition. The PCB on "WC" models does not have connector J1-auxiliary, but has a single 80 pin combined SCSI I/O and DC power connector instead of the pictured 68 pin SCSI I/O, J1-auxiliary and 4 pin DC power connectors. Included among the 80 pins are the SCSI ID, Motor Start and Delayed Motor Start select functions, and the synchronous spindle master sync signal (REFIND+) and the remote LED signals. Do not use J2 and J6 for these five functions if the host uses the ones included in the 80 pin connector. The drive uses headers J6 or J1-auxiliary for drive ID determination only during a 250 ms initialization period following power-on or after a drive reset. During this initialization period, the drive control logic connects pins 2, 4, 6 and 8 to ground and checks the logic state of pins 1, 3, 5 and 7. A ground on a pin 1, 3, 5, 7 indicates an asserted low state, while an open circuit, high impedance or +5 V indicates a negated high state. The drive user can install jumper plugs to connect pins 2, 4, 6 and 8 to pins 1, 3, 5 and 7, respectively, in the desired ID pattern. The drive only connects ground to pins 2, 4, 6 and 8 during the 250 ms initialization period. The user may install a cable on J6 or J1-auxiliary in order to connect the drive ID pattern to pins 1, 3, 5 and 7 through some external switching circuit. The drive ID should be applied for at least the 250 ms period. During the remaining operational time of the drive, the drive does not poll pins 1, 3, 5 and 7 for drive ID, unless a reset occurs. See Note [4] for information on the use of pins 2, 4, 6 and 8 during non-initialization periods. During non-initialization periods when the drive does not connect ground to pins 2, 4, 6 and 8, these pins can be used for non-drive ID functions. Therefore, instead of using jumper plugs on J1-auxiliary to estab-lish drive ID, a cable can be connected to either J6 or J1-auxiliary to connect the drive activity (busy) LED and make parallel connections of pins 1, 3, 5 and 7 to external drive ID switching or jumpering circuits. If connected pin 8 lights the drive busy LED when the drive connects ground to that pin. Connection can be made to pin 6 to conduct the synchronized spindle reference signal, REFIND+ to the host and to other Seagate disk drives. Spindle synchronization typically works effectively only if all drives connected through pin 6 are identical in make and model. During the 250 ms initialization period the LED lights and the REFIND+ signal goes to 0 V. J6 can be used to establish drive ID using jumpers (or remote ID selector) and a cable can be plugged simultaneously to J1-auxiliary to connect to the drive activity (busy) LED and the synchronized spindle signal SSP. The vice-versa arrangement is possible also. Two separate drive ID determining locations should not be used, however. These jumper positions apply to model ST12400W only. This jumper position applies to models ST12400W and ST12400WD only. These signals are also on J1. The J2 and J6 jumper headers are not used if the J1 signals are used. Drive is probably shipped with this jumper installed, but it should be removed if the system uses REFIND+ on J1-37. These jumper positions do not apply to "WC" models. J2 Jumper Installation |Jumper Function Description -------------+---------------------------------------------------- RES | Off/On |Reserved. Default is no jumper installed. -------------+---------------------------------------------------- DS ME | Off Off |Spindle starts immediately after power up - Default |setting. -------------+---------------------------------------------------- Off On |Drive spindle does not start until Start Unit command |received from host. -------------+---------------------------------------------------- On Off |Spindle Startup is delayed by SCSI ID times 12 seconds |after power is applied, i.e., drive 0 spindle starts |immediately when DC power connected, drive 1 starts |after 12 second delay, drive 2 starts after 24 second |delay, etc. -------------+---------------------------------------------------- On On |Drive spindle starts when Start Unit command received |from host. Delayed start feature is overridden and does |not apply when ME jumper is installed. | -------------+---------------------------------------------------- WP | On |Entire drive is write protected. -------------+---------------------------------------------------- Off |Drive is not write protected. Default is no WP jumper |installed. | PE | On |Parity checking and parity error reporting by the drive |is enabled. Default is PE jumper installed. -------------+---------------------------------------------------- Off |Drive does not report result of parity checking to |host. J2 Jumper Installation Jumper Function Description TE (ST12400W only) On With the jumper installed, the On-board (non-removable) terminator circuits are enabled (connected to the I/O lines). Default is jumper installed. Off Terminator circuits not connected to I/O lines. TP TP Off Off No terminator power is connected to drive terminators or SCSI bus I/O pin 26. On Off Drive supplies its own terminator power only. Jumper on this position is factory default. Off On Drive supplies power to I/O pin 26 of SCSI bus; none to internal terminators. When drives have differential I/O circuits, a jumper on the right TP position may be needed to power external terminators (see system documentation). The ST12400WD drive has differential I/O circuits which have no terminator circuits on the drive. The ST12400WC drive has no provisions for terminators and no provisions for terminator power in the 80 pin I/O connector. The TP jumpers do not apply to model ST12400WC. On On Drive supplies terminator power to itself (internal connection) and to I/O pin 26 of SCSI bus. This is a legal jumper setting. TP Position A On This horizontally positioned jumper across the two TP positions nearest PCB edge, connects terminator power from SCSI bus I/O pin 26 to the drive's internal terminators (for Model ST12400W only). Off See above explanations for TP jumpers. J1-Auxiliary, J6 Jumper Installation Jumper Function Description A3 ,A2 ,A1 ,A0 Drive ID on SCSI Bus (J1-auxiliary or J6 may be used as the ID circuits are wired in parallel). The drive ID is binary coded positionwise i.e., jumper in position A3 is drive ID 8, A2 is drive ID 4, position A1 is ID 2, position A0 is ID 1 and no jumpers is ID 0. Default is ID = 0. Both J1- auxiliary and J6 should not be used at the same time, because at some future time when the ID is changed the user could fail to configure both J1-auxiliary and J6 the same. Model ST12400WC does not have J1-auxiliary. SSP Used only as a cable connection for the reference index signal (REFIND+) (J1-6A and J6 Pin 6, bottom) for sync spindle feature. J1-10A or J6-10 provides ground. When no cable is connected, no jumpers should be installed. Factory default is no jumper installed. If a jumper is installed between pins 5 and 6 it will erroneously enable Drive ID bit A2. Synchronized spindles interface ------------------------------- The Synchronized Spindles Interface (SSI) allows several drives operating from the same host to operate their spindles at a synchronized rotational rate. Spindle synchronization typically works effectively only if all drives connected to the REFIND+ signal are identical in make and model. Electrical description ---------------------- The electrical interface consists of one digital TTL reference index signal and ground. The reference index signal (REFIND+) is an output if the drive is configured as a master and is an input otherwise. The reference index signal is connected from drive to drive in a daisychain fashion. Termination ----------- The reference index signal (REFIND+) is terminated with a 2K ohm resistor. Each drive has a termination resistor located on the Main PCB. The terminator resistor is not removable and is always in the circuit. Physical interface ------------------ They are 12 pin, 6 jumper position gold header type connectors. Pins 6 and 10 are used for connecting the Reference Index signal from drive to drive. Pin 6 is REFIND+ and Pin 10 is ground. Either J1-auxiliary or J6 may be used. On "WC" models REFIND+ is J6-6 and on J1-37. ********************************************************************** I N S T A L L ********************************************************************** SEAGATE ST12400W/WD/WC PRODUCT MANUAL 77767457 REV. C 17/03/1995 Notes on installation ===================== Installation direction ---------------------- horizontally vertically +-----------------+ +--+ +--+ | | | +-----+ +-----+ | | | | | | | | | +-+-----------------+-+ | | | | | | +---------------------+ | | | | | | | | | | | | | | | | | | +---------------------+ | +-----+ +-----+ | +-+-----------------+-+ +--+ +--+ | | | | +-----------------+ The drive will operate in all axis (6 directions). Installation ------------ The drive is designed, manufactured, and tested with a "Plug in and Play" installation philosophy. This philosophy minimizes the requirements for highly trained personnel to integrate the drive into the OEM's system, whether in a factory or field environment. The drive has been low level formatted at the factory and need not be reformatted. Service tools ------------- No special tools are required for site installation or recommended for site maintenance. The depot repair philosophy of the drive precludes the necessity for special tools. Field repair of the drive is not practical since there are no user purchasable parts in the drive. Product Warranty ---------------- Beginning on the date of shipment to customer and continuing for a period of five years, Seagate warrants that each product (including components and sub-assemblies) or spare part that fails to function properly under normal use due to defect in materials on workmanship or due to non conformance to the applicable specifications will be repaired or replaced, at Seagate's option and at no charge to customer, if returned by customer at customer's expense to Seagate's designated facility in accordance with Seagate's Warranty Procedure. Seagate will pay for transporting the repaired or replacement item to customer. For more detailed warranty information refer to the Standard terms and conditions of Purchase for Seagate products. Shock ----- a. Operating The drive, as installed for normal operation, shall operate error free while subjected to intermittent shock not exceeding 10 g's at a maximum duration of 11 ms (half sinewave). Shock may be applied in the X, Y, or Z axis. b. Nonoperating The limits of nonoperating shock shall apply to all conditions of handling and transportation. This includes both isolated drives and integrated drives. The drive subjected to nonrepetitive shock not exceeding 60 g's at a maximum duration of 11 ms (half sinewave) shall not exhibit device damage or performance degradation. Shock may be applied in the X, Y, or Z axis. Cooling ------- Cabinet cooling must be designed by the customer so that the ambient temperature immediately surrounding the drive will not exceed temperature conditions. Specific consideration should be given to make sure adequate air circulation is present around the PCBs to meet the requirements. Drive mounting -------------- When mounting the drive using the bottom holes care must be taken to ensure that the drive is not physically distorted due to a stiff non-flat mounting surface. The allowable mounting surface stiffness is 80 lb/in (14.0 N/mm). The following equation and paragraph define the allowable mounting surface stiffness: K*x = 80 lb (14.0 N) where 'k' represents the mounting surface stiffness (units of lb/in or N/mm), and, 'k' represents the out-of-plane mounting surface distortion (units of inches or millimetres). The out-of-plane distortion ('x') is deter-mined by defining a plane with three of the four mounting points fixed and evaluating the out-of-plane deflection of the fourth mounting point when a known force is applied to the fourth point. General cable characteristics ----------------------------- In general, cables having the characteristic impedance's given above are not available; however, impedance's that are somewhat lower are satisfactory. A characteristic impedance of 100 ohm 10% is recommended for unshielded flat or twisted pair ribbon cable. However, most available cables have a somewhat lower characteristic impedance. To minimize discontinuities and signal reflections, cables of different impedance's should not be used in the same bus. Implementations may require tradeoffs in shielding effectiveness, cable length, the number of loads, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered. Proper impedance matching is especially important in order to maintain adequate margin at FAST SCSI transfer rates. Cable for "W/WD" model drives ----------------------------- Only nonshielded cable is applicable. A 68 conductor flat cable or two, 34 conductor cables shall be used. Conductors should be on 50 (1.27 mm) mil centers to be used with connector. A minimum conductor size of 28 AWG should be used to minimize noise effects. Suggested nonshielded flat cable part numbers are: Flat cable - 35M-3365-68 Twisted pair - Spectra Twist in flat 455-248-68 Equivalent parts may be used. Cables for "WC" drive models ---------------------------- The 80 pin connector option is intended for use on drives that plug directly into a wall or bracket mounted connector in the host equipment. Cable mounted connectors would not be used in such a case. Installations with cable mounted connectors are not recommended. Mating connectors for model ST12400W/WD --------------------------------------- The nonshielded cable connector shall be a 68 conductor connector consisting of two rows of 34 male contacts with adjacent contacts 1.27 mm (0.050 inch) apart. Recommended Mating Connector Part Numbers for above flat cable are: Closed end Amp Model 749925-5 (50 mil conductor centers for (for cable ends) 28 or 30 AWG wire) This connector can only be used on cable ends. Open end Amp limite 88-5870-294-5 W/O Strain Relief, (25 mil conductor centers, 30 AWG wire). Use either on cable ends or in cable middle section for daisychain installations. The disc drive device connector is a nonshielded 68 conductor connector consisting of two rows of 34 female pins with adjacent pins 1.27 mm (0.050 inches) apart. The connector is keyed by means of its shape. Mating connectors for "WC" models --------------------------------- The non-shielded connector shall be an 80 conductor connector consisting of two rows of 40 contacts with adjacent contacts 50 mils (1.27 mm) apart. The connector is keyed by its shape. J2 Jumper plug part number -------------------------- Option select header connector J2 on the PCB uses an unusual type of jumper, its part number is given here for reference: Molex 52747-0211 (Seagate P/N 77670952). Recommended PCB or bulkhead mounted connectors are: Straight-in (most commonly used): Right angle to PCB connector: Seagate P/N: 77678703 Seagate P/N: 77678559 Amp US P/N: 2-557103-1 Amp US P/N: 2-557101-1 Amp Japan P/N: 5-175475-9 Amp Japan P/N: 5-175474-9 Grounding --------- Signal ground (PCBA) and HDA ground are connected together in the ST12400Wx drive and cannot be separated by the user. The equipment in which the drive i smounted is connected directly to the HDA and PCB with no electrically isolating shock mounts. If itis desired for the system chassis to not be connected to the HDA/PCBA ground, the systems integrator or user must provide a nonconductive (electrically isolating) method of mounting the drive in the host equipment. DC cable and connector ---------------------- The model ST12400W/WD drive receives DC power through a 4 pin connector mounted at the rear of the main PCB. Recommended part numbers of the mating connector are listed below, but equivalent parts may be used. Mating connector parts ---------------------- Type of cable Connector Contacts (20-14 AWG) 14 AWG AMP 1-480424-0 AMP 60619-4 (Loose Piece) AMP 61117-4 (Strip) The model ST12400WC requires no extra DC power cable since both DC power and SCSI I/O signals are all in the single 80 pin connector. Physical characteristics ------------------------ This section defines the connectors, cables, signals, terminators and bus timing needed to implement SCSI. Physical description -------------------- The model W and WD drives may be daisychained together or with other compatible SCSI devices using a common cable. Both ends of the cable must be terminated. Model ST12400 wide drives do not have on-board terminator circuits. The ST12400WD drive implements differential drivers and receivers. The model ST12400W/WC drive implements single ended drivers and receivers. All signals are common between all SCSI devices. The drive may be daisychained only with SCSI devices having the same type drivers and receivers. Devices having single ended interface circuits cannot be on the same daisychain with devices having differential interface circuit. A maximum of 16 SCSI devices (including the Host) may be daisychained together. The SCSI Devices at both ends of the daisychain are to be terminated. Intermediate SCSI devices shall not be terminated. Remove or disable (whichever is applicable) the terminators. Do not remove the terminator power source selector jumper TP. "NC" model drives plug into PCB or bulkhead connectors in the Host. They may be connected in a daisy-chain by the host backplane wiring or PCB circuit runs that have adequate DC current carrying capacity to support the number of drives plugged into the PCB or bulkhead connectors. A single 80 pin I/O connector cannot support the DC current needs of several drives, so no daisy-chain cables should be used. A single drive connected via a cable to a host 80 pin I/O connector is not recommended. Single ended I/O circuits ("W" models) -------------------------------------- The maximum total cable length for use with "W" model drives (single ended I/O driver and receiver circuits) shall be 6 metres (19.7 ft.) when operating at line data transfer rates of 5 MBytes/sec or less, and 3 metres (9.85 ft.) when operating at transfer rates greater than 5 Mbytes/sec (FAST SCSI). A stub length of no more than 0.1 metre (0.33 ft.) is allowed off the mainline interconnection with any connected equipment. An ideal impedance match with cable terminators implies a cable characteristic impedance of 132 ohms. Differential I/O circuits ("WD" models) --------------------------------------- The maximum total cable length for use with drives having differential I/O drivers and receiver circuits shall be 25 metres (82 ft.). A stub length of no more than 0.2 metre (0.66 ft.) is allowed off the mainline interconnec-tion with any connected equipment. An ideal impedance match with cable terminators implies a cable characteristic impedance of 122 ohms. ********************************************************************** F E A T U R E S ********************************************************************** SEAGATE ST12400W/WC/WD PRODUCT MANUAL 77767457 REV. C 17/3/1995 Scope ----- This specification describes the Seagate Technology, Inc. Hawk 2 family Model ST12400 Wide SCSI bus Disc Drive. This high capacity, high performance member of the Seagate 3.5 inch rigid disc family has a new HDA (Head/Disc Assembly) design having improvements over previous 3.5-inch Seagate models. It has an embedded SCSI controller. The Model Hawk 2 Family (Wide bus) drive interface is defined for functional compatibility to a subset of the Seagate SCSI-2/SCSI-3 Interface Specification 77738479, and the ANSI SCSI-2/SCSI-3 standards. The Model Hawk 2 Family (Wide bus) drives are classified as "Intelligent" peripherals. The Hawk 2 Family (Wide bus) provides Level 2 conformance (highest level) with the ANSI SCSI-1 standard. General description ------------------- The drives are a member of a family of low cost, high performance, highly reliable, random access storage devices designed to meet the needs of the OEM marketplace. The drive records and recovers data on 3.7 inch (95 mm) fixed discs. The drive supports the Small Computer System Interface (SCSI-1, SCSI-2 and SCSI-3) as described in the ANSI SCSI Interface Specifications to the extent described in this product specification (Volume 1). This manual defines the product performance characteristics of the ST12400 wide family of drives, together with the SCSI-2/SCSI-3 Interface Product Manual P/N 77738479 (Vol. 2, Version 2) which describes the general interface characteristics of this and other families of Seagate 3.5-inch drives. The drive interface supports multiple initiators, disconnect/ reconnect, self configuring host software and automatic features that relieve the host from the necessity of knowing the physical characteristics of the targets (logical block addressing is used). The Head/Disc Assembly (HDA) is environmentally sealed at the factory. Air recirculates within the HDA through a nonreplaceable filter to maintain a contamination free head/disc environment. NEVER disassemble the Head/Disc Assembly (HDA). This exploded view is for information only. Do not attempt to service items in the sealed environmental enclosure (heads, media, actuator, etc.) as this requires special facilities. The drive contains no parts replaceable by the user. The drive warranty is voided if the HDA is opened. The ST12400 wide family drives use a dedicated landing zone at the innermost radius of the media to eliminate the possibility of destroying or degrading data by landing in the data zone. The drive automatically goes to the landing zone when the power is removed. The ST12400 wide family drives incorporate an automatic shipping lock which prevents potential damage to the heads and discs that result from movement during shipping and handling. The shipping lock disengages when power is applied to the drive and the head load process begins. The ST12400 wide family drives decode Track 0 location from the dedicated servo surface to eliminate mechanical transducer adjustments and related reliability concerns. The ST12400 wide family drives use a high performance actuator assembly that consists of a low inertia, balanced, patented, straight arm design that provides excellent performance with minimum power dissipation. Optional accessories (user installed) ------------------------------------- The following accessories are available. All kits may be installed in the field. - Front Panel Kit (with green LED) - Single Unit shipping pack kit - Installation Guide P/N 77767465 - Adapter Accessory Frame Kit P/N 75790701 (adapts 3.5-inch ST12400W/WD drive to fit in 5.25-inch drive mounting space, does not work for model ST12400WC). Prefetch/multi-segmented cache control -------------------------------------- The drive provides prefetch (read look-ahead) and multi-segmented cache control algorithms that in many cases can enhance system performance. "Cache" as used herein refers to the drive buffer storage space when it is used in "cache" operations. To select prefetch and cache features the host sends the Mode Select command with the proper values in the applicable bytes in Mode Page 08h*. Prefetch and cache operation are independent features from the standpoint that each is enabled and disabled independently via the Mode Select command. Cache operation --------------- In general, 240 kBytes of the 256 kBytes of physical buffer space in the drive can be used as storage space for cache operations (984 KB of 1 MB for drives having 1 MB optional buffer). The buffer can be divided into logical segments (Mode Select Page 08h, byte 13) from which data is read and to which data is written. The drive maintains a table of logical block disk medium addresses of the data stored in each segment of the buffer. If cache operation is enabled (RCD bit = 0 in Mode Page 08h, byte 2, bit 0. See SCSI Interface Product Manual), data requested by the host with a Read command is retrieved from the buffer (if it is there), before any disc access is initiated. If cache operation is not enabled, the buffer (still segmented with required number of segments) is still used, but only as circular buffer segments during disc medium read operations (disregarding Prefetch operation for the moment). That is, the drive does not check in the buffer segments for the requested read data, but goes directly to the medium to retrieve it. The retrieved data merely passes through some buffer segment on the way to the host. All data transfers to the host are in accordance with "buffer-full" ratio rules. See explanations associated with Mode page 02h (disconnect/ reconnect control) in the SCSI Interface Product Manual. Caching write data ------------------ Write caching is a write operation by the drive that makes use of a drive buffer storage area where the data to be written to the medium is stored in one or more segments while the drive performs the write command. Write caching is enabled along with read caching. For write caching, the same buffer space and segmentation is used as set up for read functions. The buffer segmentation scheme is set up or changed independently, having nothing to do with whether or not read and write caching is enabled or disabled. When a write command is issued, the cache is first checked to see if any logical blocks that are to be written are already stored in the cache from a previous read or write command. If there are, the respective cache segments are cleared. The new data is cached for subsequent Read commands. If the number of write data logical blocks exceeds the size of the segment being written into when the end of the segment is reached, the data is written into the beginning of the same cache segment, overwriting the data that was written there at the beginning of the operation. However, the drive does not overwrite data that has not yet been written to the medium. Synchronized spindle operation ------------------------------ The synchronized spindles operation allows several drives operating from the same host to operate their spindles at the same synchronized rotational rate. Drives operating in a system in synchronized mode can increase the system capacity and transfer rate in a cost effective manner. For "W" and "WD" models the interface consists of a twisted pair cable that connects the drives in the synchronized system in a daisy-chain configuration. For "WC" models the reference index signal ("SYNC") signal is on pin J1-37 of the 80-pin I/O connector. Master/Slave operation is autoarbitrated by each drive after head load. Alternatively, each drive in the system can be configured by the host (using the Mode Select command Rigid Disc Drive Geometry page) to operate in either the master or slave mode. After loading heads, a drive autoarbitrates for occurences of the Reference Index Signal (REFIND+). If the drive detects no REFIND+ signal on the line, it assumes master status and begins generating the REFIND+ signal. This signal will not be visible on the line until the last drive has powered up, since any unpowered drive holds the line low. Using Mode Select command, drives can be re-configured by the host to be master or slave any time after the last drive has powered up. The master provides the reference signal to which all other drives phase lock, including the master. The master can be a drive or the host computer. All the drives may be configured as slaves, allowing the host to provide the REFIND+ signal. All drives default to the synchronized mode when powered up, unless J6 pins 5 and 6 are jumpered. Each drive can be configured (jumpered) for the non-synchronized mode in which it ignores any reference signal that might be present. The connection of the synchronized reference signal to the host is required only if the host is to provide the reference signal. If the host does not provide the reference signal, the host should not be connected. Media description ----------------- The media used on the drive has a diameter of approximately 95 mm (approximately 3.7 inches). The aluminum substrate is coated with a thin film magnetic material and overcoated with a proprietary protective layer for improved durability and environmental protection. Defect and error management --------------------------- The drive, as delivered, complies with this specification. The read error rate and specified storage capacity are not dependent upon use of defect management routines by the host (initiator). Defect and error management in the SCSI system involves the drive internal defect/error management and SCSI systems error considerations (errors in communications between Initiator and the drive). Tools for use in designing a defect/error management plan are briefly outlined in this section, with references to other sections where further details are given. Drive internal defects/errors ----------------------------- Identified defects are recorded on the drive defects list tracks (referred to as the primary or ETF defect list). These known defects are reallocated during the initial drive format operation at the factory. Data correction by ECC can be applied to recover data from additional flaws if they occur. SCSI systems error considerations --------------------------------* Information on the reporting of operational errors or faults across the interface is given in SCSI Interface Product Manual. Message Protocol System is described in the SCSI Interface Product Manual. Several of the messages are used in the SCSI systems error management system. The Request Sense command returns information to the host about numerous kinds of errors or faults. The Receive Diagnostic Results reports the results of diagnostic operations performed by the drive. Status returned by the drive to the Initiator is described in the SCSI Interface Manual. Status reporting plays a role in the SCSI systems error management and its use in that respect is described in sections where the various commands are discussed. Electrical description ---------------------- The ST12400W/WC models use single ended interface signals. These signals must be terminated with 110 ohm active termination circuits at each end of the total cable. ST12400WC drives have no provisions for terminators on the PCB. On model ST12400WC some method of external termination must be provided by the user, systems integrator or the host equipment manufacturer. On ST12400W drives terminator power can be supplied from the drive to the I/O connector by the drive by properly positioning the TP jumper plug and the J2 option select header. Single Ended circuits use open collector or three state drivers. The model ST12400WD uses differential interface signals and each of these must be terminated at each end of the total cable with 330 ohms to +5 V and 330 ohms to ground with 150 ohms between each differential pair. All I/O circuits are open collector, three state drivers. ST12400WD drives have no provisions for adding terminators on the PCB. Some method of external termination must be provided (where needed) by the user, systems integrator or host equipment manufacturer. The ST12400WD model drive can furnish terminator power to the SCSI I/O cable by properly positioning jumper plug TP. Single ended drivers/receivers ------------------------------ Transmitter characteristics Single ended drives use an ANSI SCSI compatible open collector single ended driver. This driver is capable of sinking a current of 48 mA with a low level output voltage of 0.4 volt. Receiver characteristics Single ended drives use an ANSI SCSI single ended receiver with hysteresis gate or equivalent as a line receiver. Differential drivers/receivers ------------------------------ The drive has no provisions for terminator circuits on the drives. Differential signals All differential interface signals consist of two lines denoted +SIGNAL and -SIGNAL. A signal is true when +SIGNAL is more positive than -SIGNAL, and a signal is false when -SIGNAL is more positive than +SIGNAL. All assigned signals shall be terminated at each end of the cable. Drive user, systems integrator or OEM manufacturer must provide some external means of termination. Terminator power can be supplied by the drive to the I/O cable by properly positioning a jumper plug. Output characteristics Each signal driven by differential interface drives shall have the following output characteristics when measured at the disc drive SCSI connector: Low-level output voltage* = 2.0 V maximum at Low-level output current = 55 milliamps. High-level output voltage* = 3.0 V minimum at High-level output current = -55 milliamps Differential voltage = 1.0V minimum with common-mode voltage ranges from -7 V dc to +12 V dc. These voltages shall be measured between the output terminal and the SCSI device's logic ground reference. The output characteristics shall additionally conform to EIA RS-485-1983. Input characteristics Each signal received by differential interface drives shall have the following input characteristics when measured at the disc drive SCSI connector: Input current on either input = +2.0 milliamps maximum (includes both receivers and passive drivers). This requirement shall be met with the input voltage varying between -7 V dc and +12 V dc, with power on or off, and with the hysteresis equaling 35 mv, minimum. The input characteristics shall additionally conform to EIA RS-485-1983. Terminator requirements ----------------------- Drive I/O termination is not provided internally on ST12400WD or ST12400WC drives. Terminator circuits, must be provided in some manner external to the ST12400WD/WC drives by the user, systems integrator or OEM manufacturer. It is highly recommended that ANSI SCSI-2 Standard's Alternative 2 termination (active termination) be used for single-ended ST12400W and ST12400WC applications, especially if the bus will be operated at transfer rates above 5 Mbytes/sec. The ST12400W provides on-board active termination that can be disabled by removal of the enable jumper TE. Power for the external terminators may be taken from the drive by installing a jumper plug on one of the J2-TP. If the TP jumper is not installed terminator power must be supplied by some other source. All single initiator/single target (nondaisychain) applications require that the Initiator and disc drive be terminated. Daisychain applications require that only the units at each end of the daisychain be terminated. All other peripherals on the chain should not be terminated. Note. Where terminators are not required, remove external terminator modules or disable terminators on the model ST12400W by removing the TE jumper from header J2. Removal of terminator power source selection jumper TP does not disconnect the terminators from the circuit. Note. ACTIVE TERMINATORS ARE HIGHLY RECOMMENDED FOR USE IN THE DAISYCHAIN AS DESCRIBED ABOVE. ACTIVE AND PASSIVE TERMINATORS SHOULD NOT BE MIXED ON THE SAME SCSI BUS. Terminator power ---------------- The model ST12400W/WD drives may be configured to provide terminator power via pins 17, 18, 51 and 52 of the SCSI Bus, to supply power to the SCSI bus. The drive can provide power both to external terminators at the drive end and to the SCSI Bus terminator power lines to provide power for terminators at the other end of the I/O cable. SCSI devices providing terminator power (TERMPWR) shall have the following characteristics: V TERM = 4.50V to 5.25V 800 mA min source drive capability 1.0 A maximum The model ST12400WC drive cannot furnish terminator power, because no pins in the 80 pin I/O connector are devoted to terminator power. Options ------- All options are incorporated or packaged at the manufacturing facility. Front panel ----------- The normal front panel available is black plastic. Other panel colors may be special ordered. Each panel has a single rectangular green LED indicator lens which, when glowing, indicates the drive is selected. ********************************************************************** G E N E R A L ********************************************************************** SEAGATE SCSI Interface requirements ---------------------- How to use this interface manual This specification is designed to provide a universal detailed description of the SCSI interface for those disc drive products whose Product Manuals (Volume 1) do not contain the details of how the SCSI interface is implemented by that drive. Note: Volume 1 Product Manuals have tables in Section 11 that specify which SCSI-1 or SCSI-2/SCSI-3 features they implement, what the default parameters are for the various features they implement and which parameters are changeable and which are not. No method exists at present to inform an initiator if a target supports "SCSI-3" features as opposed to only SCSI-2 features. A few "SCSI-3" features are supported by Seagate drives, but no attempt has been made herein to differentiate between SCSI-2 and "SCSI-3" features. Therefore, when an Inquiry command reports what the ANSI approved version of the drive is, it reports either SCSI-1 or SCSI-2, where "SCSI-2" means SCSI-2 features plus some "SCSI-3" features. No attempt is made in this universal specification to specify which descriptions or tables apply to SCSI-1 and which to SCSI-2 or SCSI-3. The combination of this general specification with the details in the Section 11 tables of the individual drive Product Manual (Volume 1) provides a description of the individual drive implementation of the SCSI interface. This interface manual is not intended to be stand-alone text on SCSI-1 or SCSI-2/SCSI-3 features. Reference must be made back to the individual drive Product Manuals to find out what are SCSI-1 and what are SCSI-2/SCSI-3 features. This specification is Volume 2 of a set of manuals that is made up of separate drive Product Manuals (Volume 1) and this manual. This Volume 2 Manual is referenced by other Volume 1 Product Manuals representing the drives listed below. Product Manuals for the following models reference this volume: ST11200N/ND/NC, ST1980N/ND/NC, ST1830N, ST1950N, ST3500N, ST3600N, ST3610N/ND/NC, ST12400N/ND/NC, ST12400 Wide, ST11900N/ ND/NC, ST31200N/ND/NC, ST31200 Wide, ST11950N/ND, ST11950W/WD, ST12450W/WD, ST12550N/ND, ST12550W/WD, ST15150N/ND, ST15150W/WD, ST3655N, ST3550W, ST3390N and ST3285N, ST32430N/ND/NC, ST32430W/WD/WC, ST15230N/ND/NC, ST31250N/ND, ST31250W/WD/WC, ST32151N, ST31051N, ST32550N/ND, ST32550W/WD/WC, ST3471N, ST410800N/ND, ST410800W/WD. General interface description ----------------------------- This Product Manual describes the Seagate Technology, Inc. subset of the SCSI (Small Computer Systems Interface) as implemented on the Seagate built disc drives listed above. The interface is compatible with the SCSI Interface Specifications of the ANSI SCSI-1 standard, the ANSI SCSI-2 Standard and the common command set (CCS) document, Revision 4.B. The disc drives covered by this Product Manual are classified as "Intelligent" peripherals. The Seagate SCSI interface described herein consists of a 9 or 18 bit bidirectional bus (8 data + 1 parity or 16 data + 2 parity) plus 9 control signals supporting multiple initiators, disconnect/ reconnect, self configuring host software, automatic features that relieve the host from the necessity of knowing the physical architecture of the target (logical block addressing is used), and some other miscellaneous features. The SCSI physical interface uses either single ended drivers and receivers or differential drivers and receivers and uses asynchronous or synchronous communication protocols. The bus interface transfer rate for asynchronous or synchronous is given in individual disc drive Volume 1 Product Manuals. The bus protocol supports multiple initiators, disconnect/reconnect, additional messages plus 6 byte and 10 byte Command Descriptor Blocks. Unless specified otherwise in the individual drive Product Manuals (Vol. 1), the disc drive is always a target, and never an initiator. For certain commands, which may or may not be supported by a particular drive model, the drive must act as an initiator, but does not otherwise do so. For purposes of this specification, "disc drive" may be substituted for the word "target" wherever "target" appears. GLOSSARY -------- Arbitration - SCSI bus phase wherein SCSI devices try to gain control of the SCSI bus to operate as an initiator or target Byte - This term indicates an 8 bit hexadecimal construction. Command Descriptor Block (CDB) - The structure used to communicate requests from an initiator to a target. Connect - The function that occurs when an initiator selects a target to start an operation. Disconnect - The function that occurs when a target releases control of the SCSI bus, allowing it to go to the Bus Free phase. FRU (Field Replaceable Unit) - An assembly that is believed faulty based on test results. A value of 00h indicates an unknown cause or the end of a list of known possible causes. Nonzero values have product unique meanings. Initiator - A SCSI device (usually a host system) that requests an operation to be performed by another SCSI device. Intermediate Status - A status code sent from a target to an initiator upon completion of each command, except the last command, in a set of linked commands. I/O Process - An I/O process consists of one initial connection and zero or more reconnections, all pertaining to a single command or group of linked commands. More specifically, the connection(s) pertain to a nexus as defined below in which one or more command descriptor blocks are usually transferred. An I/O process begins with the establishment of a nexus. An I/O process normally ends with the BUS Free phase following successful transfer of a COMMAND COMPLETE, ABORT, ABORT TAG, or CLEAR QUEUE message. An I/ O process also ends when a hard RESET condition occurs, an unexpected BUS FREE phase occurs, or when the BUS FREE phase occurs following a BUS DEVICE RESET message. I T nexus - A nexus prior to the successful receipt of an IDENTIFY message, at which time the nexus is changed to an I T L nexus. (See glossary word "Nexus"). I T L nexus - A nexus that exists between an initiator and a Logical Unit. This relationship replaces the prior I T nexus. (See glossary word "Nexus"). I T L Q nexus - A nexus between an initiator, a Logical Unit, and a queue tag following the successful receipt of one of the QUEUE messages. This relationship replaces the prior I T L nexus. (See glossary word "Nexus"). Logical Unit - A physical device or virtual device addressable through a target. The disc drive is a target but also a Logical Unit. Logical Unit Number - An encoded three bit identifier for the logical unit. The disc drive is considered Logical Unit number zero. LSB - Least significant byte MSB - Most significant byte ms - millisecond LUN - Logical unit number mm - Millimetre SCSI bus -------- This manual discusses only the "logical" and timing characteristics of the SCSI system and interface. The SCSI bus physical characteristics (voltages, connector configurations, pinouts, etc.) are given in the individual disc drive Product Manuals (Volume 1) Section "Interface requirements", which covers all of the interface requirements and SCSI features supported by the drive described in the particular Product Manual being referenced. Communication on the SCSI Bus is allowed between only two SCSI devices at a time. Some Seagate drives support systems with a maximum of eight SCSI devices including the host computer(s) connected to the SCSI bus. Some Seagate drives support systems with a maximum of sixteen SCSI devices on the SCSI bus. Each SCSI device has a SCSI ID Bit. The SCSI ID is assigned by installing from 0 to 3 (8 device systems) jumper plugs or 0-4 (16 device systems) jumper plugs onto a connector in a binary coded configuration during system configuration. Some drive models have an interface that includes the SCSI bus ID lines, so that the host can set the drive ID over the interface. See individual disc drive Product Manual, Section "Option/configuration headers". When two SCSI devices communicate on the SCSI Bus one acts as an initiator and the other acts as a target. The initiator (typically a host computer) originates an operation and the target performs the operation. The disc drive always operates as a target, unless specified otherwise (i.e., certain commands are supported) in the individual drive Product Manual. The Host Adapter/Initiator must be identified by one of the eight SCSI Device Addresses. Make sure that none of the devices on the SCSI bus have duplicate addresses. Certain SCSI bus functions are assigned to the initiator and certain SCSI bus functions are assigned to the target. The initiator will select a particular target. The target will request the transfer of Command, Data, Status or other information on the data bus. Information transfers on the data bus are interlocked and follow a defined REQ/ACK Handshake protocol. One byte of information will be transferred with each handshake. Synchronous data transfers do not require a one for one interlocking of REQ/ACK signals, but the total number of REQ pulses in a particular data transfer event must equal the total number of ACK pulses. The disc drive supports single initiator, single target; single initiator, multiple target; multiple initiator, single target; or multiple initiator, multiple target bus configurations. SCSI bus signals ---------------- There are ten control and eighteen data signals, as listed below: - BSY - C/D - MSG - DIFFSENS - SEL - I/O - REQ - DB(7-0, P); DB(15-8,P1) - ACK - ATN - RST Some drive models have a single 80 pin I/O connector that contains additional interface lines that carry drive configuration select signals. These are peculiar to certain drives and are not SCSI standard signals. These are described in the drive model's Volume 1 Product manual, but not here. The 28 SCSI standard signals are described as follows: BSY (Busy) - An "OR-tied" signal to indicate the bus is being used. SEL (Select) - A signal used by an initiator to select a target, or by a target to reselect an initiator. C/D (Control/Data) - A signal driven by a target to indicate whether Control or Data information is on the Data Bus. Assertion indicates Control. I/O (Input/Output) - A signal driven by a target to control the direction of data movement on the Data Bus with respect to an initiator. Assertion indicates input to the initiator. This signal also distinguishes between Selection and Reselection phases. MSG (Message) - A signal driven by a target during the Message phase. REQ (Request) - A signal driven by a target to indicate a request for REQ/ACK data transfer handshake. ACK (Acknowledge) - A signal driven by an initiator to indicate an acknowledgment for a REQ/ACK data transfer handshake. ATN (Attention) - A signal driven by an initiator to indicate the Attention condition. It is used to request to send a message out to the target. If an initiator asserts ATN while asserting SEL it indicates to the target that the initiator supports messages other than command complete. RST (Reset) - An "OR-tied" signal that indicates the Reset condition. DIFFSENS (Differential Sense) - When the drive has differential SCSI I/O circuits, the DIFFSENS signal disables the drive s differential driver/receiver circuits if the SCSI I/O cable is plugged in upside down, or if a single-ended SCSI I/O cable is plugged into a differential I/O drive. Disabling the differential I/O drivers/ receivers is necessary to prevent burning them out if a grounded I/O line is connected to any of the differential circuit outputs, which are at a positive voltage (+2 V or +3 V) when not disabled. DB(7-0,P) and DB(15-8,P1) (Data Bus) - Sixteen data bit signals, plus parity bit signals form a Data Bus. DB(7) is the most significant bit and has the highest priority during the Arbitration phase (on both eight and sixteen device systems). Bit number significance, and priority decrease downward to DB(0), and then from DB15 down to DB8 (DB0 is higher than DB15). A data bit is defined as one when the signal is asserted and is defined as zero when the signal is negated. Data parity DB(P) and DB(P1) is odd - The use of parity is a system option. The disc drive always checks parity on the data bits, but has the capability to enable/disable parity error reporting to the host. See configuration selection in the applicable Product Manual. Parity checking is not valid during the Arbitration phase. Greater detail on each of the SCSI Bus signals is found in the following sections. Drive Select ------------ For SCSI ID selection install drive select jumpers as shown in configuration selection figure in applicable Product Manual. Refer to section 10 of the individual drive Product Manual for the location of the drive select header. The disc drive using the eight bit data interface can have one of eight ID bits selected by installing 0 to 3 jumpers in a binary coded configuration on the drive select header. Drives using the 16 bit data interface can have one of sixteen ID bits selected by installing 0 to 4 jumpers in a binary coded configuration on the drive select header. Signal Values ------------- Signals may assume true or false values. There are two methods of driving these signals. In both cases, the signal shall be actively driven true, or asserted. In the case of OR-tied drivers, the driver does not drive the signal to the false state, rather the bias circuitry of the bus terminators pulls the signal false whenever it is released by the drivers at every SCSI device. If any driver is asserted, then the signal is true. In the case of non-OR-tied drivers, the signal may be negated. Negated means that the signal may be actively driven false, or may be simply released (in which case the bias circuitry pulls it false), at the option of the implementor. OR-Tied signals --------------- The BSY and RST signals shall be OR-tied only. In the ordinary operation of the bus, these signals are simultaneously driven true by several drivers. No signals other than BSY, RST, and DB(P) are simultaneously driven by two or more drivers, and any signal other than BSY and RST may employ OR-tied or non-OR-tied drivers. DB(P) shall not be driven false during the Arbitration phase. There is no operational problem in mixing OR-tied and non-OR-tied drivers on signals other than BSY and RST. Signal sources -------------- All SCSI device drivers that are not active sources shall be in the passive state. Note that the RST signal may be sourced by any SCSI device at any time. The disc drive functions as a target. Nonarbitrating system --------------------- In systems with the Arbitration phase not implemented, the initiator shall first detect the Bus Free phase and then wait a minimum of a bus clear delay. Then, except in certain single initiator environments with initiators employing the single initiator option the initiator shall assert the desired target's SCSI ID and its own initiator SCSI ID on the Data Bus. After two deskew delays, the initiator shall assert SEL. Arbitrating systems ------------------- In systems with the Arbitration phase implemented, the SCSI device that won the arbitration has both BSY and SEL asserted and has delayed at least a bus clear delay plus a bus settle delay before ending the Arbitration phase. The SCSI device that won the arbitration becomes an initiator by releasing I/O. Except in certain single initiator environments with initiators employing the single initiator option, the initiator shall set the Data Bus to a value which is the OR of its SCSI ID bit and the target s SCSI ID bit. The initiator shall then wait at least two deskew delays and release BSY. The initiator shall then wait at least a bus settle delay before looking for a response from the target. All systems ----------- In all systems, the target shall determine that it is selected when SEL and its SCSI ID bit are true and the BSY and I/O signals are false for at least a bus settle delay. The selected target will examine the Data Bus in order to determine the SCSI ID of the selecting initiator unless the initiator employed the single initiator option. The selected target shall then assert BSY within a selection abort time of its selection; this is required for correct operation of the timeout procedure. In systems with parity implemented, the target shall not respond to a selection if bad parity is detected. Also, if more than two SCSI ID bits are on the Data Bus, the target shall not respond to selection. At least two deskew delays after the initiator detects BSY is asserted, it shall release SEL and may change the Data Bus. Single initiator option ----------------------- Initiators that do not implement the Reselection phase, and do not operate in the multiple initiator environment, are allowed to set only the target's SCSI ID bit during the Selection phase. This makes it impossible for the target to determine the initiator s SCSI ID. Selection time out procedure ---------------------------- A Selection timeout procedure is specified for clearing the SCSI bus. If the initiator waits a minimum of a selection timeout delay and there has been no BSY response from the target, the initiator shall continue asserting SEL and shall release the Data Bus. If the initiator has not detected BSY to be asserted after at least a selection abort time plus two deskew delays, the initiator shall release SEL allowing the SCSI bus to go to the Bus Free phase. SCSI devices shall ensure when responding to selection that the selection was still valid within a selection abort time of their assertion of BSY. Failure to comply with this requirement could result in an improper selection (two targets connected to the same initiator, wrong target connected to an initiator, or a target connected to no initiator). The disc drive supports systems that implement this procedure. Asynchronous information transfer --------------------------------- The target shall control the direction of information transfer by means of the I/O signal. When I/O is true, information shall be transferred from the target to the initiator. When I/O is false, information shall be transferred from the initiator to the target. If I/O is true (transfer to the initiator), the target shall first drive DB(7-0,P)* to their desired values, delay at least one deskew delay plus a cable skew delay, then assert REQ. DB(7-0,P)* shall remain valid until ACK is true at the target. The initiator shall read DB(7-0,P)* after REQ is true, then signal its acceptance of the data by asserting ACK. When ACK becomes true at the target, the target may change or release DB(7-0, P)* and shall negate REQ. After REQ is false the initiator shall negate ACK. After ACK is false, the target may continue the transfer by driving DB(7-0,P)* and asserting REQ, as described above. If I/O is false (transfer to the target) the target shall request information by asserting REQ. The initiator shall drive DB(7-0,P)* to their desired values, delay at least one deskew delay plus a cable skew delay and assert ACK. The initiator shall continue to drive the DB(7-0,P)* until REQ is false. When ACK becomes true at the target, the target shall read DB(7-0,P)*, then negate REQ. When REQ becomes false at the initiator, the initiator may change or release DB(7-0,P)* and shall negate ACK. The target may continue the transfer by asserting REQ, as described above. Synchronous data transfer ------------------------- Synchronous data transfer may be used only in the data phase if previously agreed to by the initiator and target through the message system. The messages determine the use of synchronous mode by both SCSI devices and establish a REQ/ACK offset and a transfer period. The REQ/ACK offset specifies the maximum number of REQ pulses that can be sent by the target in advance of the number of ACK pulses received from the initiator, establishing a pacing mechanism. If the number of REQ pulses exceeds the number of ACK pulses by the REQ/ACK offset, the target shall not assert REQ until the next ACK pulse is received. A requirement for successful completion of the data phase is that the number of ACK and REQ pulses be equal. The target shall assert the REQ signal for a minimum of an assertion period. The target shall wait at least the greater of a transfer period from the last transition of REQ to true or a minimum of a negation period from the last transition of REQ to false before asserting the REQ signal. The initiator shall send one pulse on the ACK signal for each REQ pulse received. The ACK signal may be asserted as soon as the leading edge of the corresponding REQ pulse has been received. The initiator shall assert the ACK signal for a minimum of an assertion period. The initiator shall wait at least the greater of a transfer period from the last transition of ACK to true or for a minimum of a negation period from the last transition of ACK to false before asserting the ACK signal. Unit attention condition ------------------------ The disc drive sets up the Unit Attention condition when it stores (within itself) a Unit Attention condition flag for each device on the SCSI bus having an initiator relationship with the disc drive, and this Unit Attention condition persists for each initiator until the condition is cleared (flag negated) by each initiator individually. The Unit Attention condition results when one of the following events occur: 1. A power-on sequence occurs. 2. A reset is generated internally by the disc drive (caused by a power glitch). 3. A Bus Device Reset message causes the disc drive to reset itself. 4. The RESET I/O line resets the disc drive. 5. An initiator changes one or more of the Mode Select parameters in the disc drive (these changes could affect one or more of the other initiators). 6. The inquiry data has been changed. 7. The mode parameters in effect for an initiator have been restored from nonvolatile memory. 8. An event occurs that requires the attention of the initiator. 9. A Clear Queue message received. 10. The Log parameters are changed. Unit Attention Condition is posted for all initiators in the system other than the one that changed the Log Parameters. The Unit Attention Parameters page (page 00h, bit 4 of byte 2) of the Mode Select Command controls whether or not a Check Condition Status is to be reported to affected initiators when a Unit Attention condition exists. The Unit Attention condition for a particular initiator is cleared when that initiator does one of the following: 1. It sends a Request Sense Command. 2. It sends any other legitimate command, with the exception of the Inquiry command. The Inquiry command does not clear the Unit Attention condition. When a Unit Attention condition flag is stored in the disc drive for an initiator, the commands that initiator issues to the disc drive operate as described in the following paragraphs. If an initiator sends an Inquiry command to the disc drive when the disc drive has stored a Unit Attention condition flag for that initiator before or after the disc drive reports Check Condition status), the disc drive shall perform the Inquiry command and shall not clear the Unit Attention condition. If an initiator sends a Request Sense command to the disc drive when a Unit Attention condition flag is stored for that initiator (before or after the disc drive reports Check Condition), the disc drive shall discard any pending sense data, report the Unit Attention Sense Key, and clear the Unit Attention condition (negate the flag) for that initiator. If an initiator issues a command other than Inquiry or Request Sense while a Unit Attention condition flag is stored for that initiator, the disc drive may or may not perform the command and report Check Condition status, depending on whether or not the Unit Attention bit is zero or one in the Unit Attention Mode Parameters page (Page 00h, bit 4 of byte 2). If a Request Sense is issued next, the Unit Attention condition is reported and cleared (flag negated) as noted in the preceding paragraph. If another command other than Request Sense or Inquiry is issued instead, the disc drive shall perform the command and return the appropriate status. The Unit Attention condition for the subject initiator is cleared (flag negated) and the sense data and flag indicating there has been a Unit Attention condition are lost.