D F H S - S 2 S U L T R A S T A . X P IBM Native| Translation ------+-----+-----+----- Form 3.5"/SLIMLINE Cylinders | | | Capacity form/unform 2255/ MB Heads 8| | | Seek time / track 8.0/ ms Sector/track | | | Controller SCSI2 SI/FAST/SCA Precompensation Cache/Buffer 512 KB SEGMENTED Landing Zone Data transfer rate MB/S int Bytes/Sector 512 10.000 MB/S ext SYNC Recording method PRML operating | non-operating -------------+-------------- Supply voltage 5/12 V Temperature *C 5 55 | -40 65 Power: sleep W Humidity % 5 90 | 5 95 standby W Altitude km -0.304 3.048| -0.304 12.192 idle W Shock g 10 | 60 seek W Rotation RPM 7200 read/write W Acoustic dBA spin-up W ECC Bit ON THE FLY MTBF h 1000000 Warranty Month Lift/Lock/Park YES Certificates CISPR22,CSA,EEC,FCC,IEC950... ********************************************************************** L A Y O U T ********************************************************************** IBM DFHS-S1X/S2X/S4X ULTRASTAR XP PRODUCT DESCRIPTION 68-Pin SCSI (Rear View) +-----------------------------------------------------+ | | | | | | | | |++---------SCSI-----------------+-Aux.---+-Power---++| ||| +------------------------1-+ |+-----1+|+-------+||| ||| |\::::::::::::::::::::::::/| ||::::::|||XXXXXXX|||| ||| +--------------------------+ |+-----2+|+-------+||| ||+------------------------------+Connect.+-4-3-2-1-+|| ++ ++ 50-Pin SCSI (Rear View) +-----------------------------------------------------+ | | | | | | | | |++---------SCSI--------------------------+-Power---++| ||| +-----------------------------------1+|+-------+||| ||| |::::::::::::::::::::::::::::::::::::|||XXXXXXX|||| ||| +------------------------------------+|+-------+||| ||+---------------------------------------+-4-3-2-1-+|| ++ ++ 80-Pin SCSI (Rear View) +-----------------------------------------------------+ | | | | | | | +---------------------------------+ | |+--------|/*******************************\|--------+| || +1--------------------------------+ || || || ++ ++ Jumper Pin locations all models (Front view) +-----------------------------------------------------+ | | | | | | | | | | |++1-----------------+-12-+--------------------------+| |||::::.:::::::::::::| oo | || |++------------------+----+--------------------------+| ++ ++ ********************************************************************** J U M P E R S ********************************************************************** IBM DFHS-S1X/S2X/S4X ULTRASTAR XP PRODUCT DESCRIPTION Jumper Setting -------------- Option Jumper Block(s) ---------------------- DFHS models contain a jumper block that can be used to enable certain features and select the SCSI ID of the drive. This jumper block is referred to as the Front Option Jumper Block due it's location on the drive (opposite the SCSI connector). This jumper block varies in pin definition based on interface type (50, 68, Differential, SCA). The Option Block connector (2 x 16) used on 50 pin models is an AMP connector (P/N 84156-4) having a pin spacing of 2mm. The Option Block connector (2 x 16) used on the 68 and 80 pin models is an AMP connector (P/N 84156-5) having a pin spacing of 2mm. 68-pin models also contain a rear option jumper block that replicates some of the functions contained in the front block. Termination Power Enable +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+ |1*|03|05|07|xx|11|13|15|17|19|21|23|25|27|29|31| | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |01|02| |2*|04|06|08|10|12|14|16|18|20|22|24|26|28|30|32| | | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+ *NOTE: PINS 1 AND 2 DO NOT EXIST IN 50-PIN MODELS! Alternate Mode -------------- Option Block Mode (Jumper shown selecting Option Block Mode) | | BIT | 3 2 1 0 --++-+-++-++-++-++ +--+--+ |XX|25|27|29|31| | | | -+XX+--+--+--+--+ |01|02| |XX|26|28|30|32| | | | +--+--+--+--+--+ +--+--+ +--+---+--+--+ Ground Option Block Mode Pin --------------------- The Option Block Mode pin is used to modify the function of the Front Option Jumper Block. When the Option Block Mode Pin is not grounded the pin function of the front Option Jumper Block will be as defined by the upper portion of the referenced figures. When the Option Block Mode Pin is grounded the pins (25, 27, 29, 31) will be redefined to control what is referred to as Alternate Mode. Alternate Mode allows tailoring of SCSI options such as boot up characteristics and other operational features on a per customer basis. 50/68 Pin Model Single Ended ---------------------------- Pin| Description ---+--------------------------------------------------------- 01 | Bit 3 (MSB) (Do not exist in 50-pin models)--+ 03 | Bit 2 --+ Address 05 | Bit 1 --+ Jumpers 07 | Bit 0 (LSB) --+ 09 | Blank Polarity 10 | Unused 11 | Auto Start 13 | +5V 14 | Enable Active Termination 15 | -Master Sync 16 | -Slave Sync 17 | External Activity LED 18 | +5V 19 | Write Protect 21 | Auto Start Delay 23 | Option Block Mode 25 | Disable T.I. Sync Negotiations 27 | Disable SCSI Parity 29 | Disable Unit Attention 31 | Customizing 50/68 Pin Model Differential ---------------------------- Pin| Description ---+--------------------------------------------------------- 01 | Bit 3 (MSB) 68-pin models only --+ 03 | Bit 2 --+ Address 05 | Bit 1 --+ Jumpers 07 | Bit 0 (LSB) --+ 09 | Blank Polarity 10 | Unused 11 | Auto Start 13 | +5V* 14 | Unused* 15 | -Master Sync 16 | -Slave Sync 17 | External Activity LED 18 | +5V 19 | Write Protect 21 | Auto Start Delay 23 | Option Block Mode 25 | Disable T.I. Sync Negotiations 27 | Disable SCSI Parity 29 | Disable Unit Attention 31 | Customizing * Pin 13 is Enable Narrow Mode on 80Pin SCA and 68Pin differential Pin 14 is Ground on 80Pin SCA and 68Pin differential NOTE Pins 2, 4, 6, 8, 12, 20, 22, 24, 26, 28, 30 and 32 are Ground. 68Pin Auxiliary Connector ------------------------- +----------------- +5V | +-------------- Enable Active Termination | | +----------- SCSI ID 3 | | | +-------- SCSI ID 2 | | | | +----- SCSI ID 1 | | | | | +-- SCSI ID 0 ++-++-++-++-++-++-+ |11|09|07|05|03|01| +--+--+--+--+--+--+ |12|10|08|06|04|02| ++-++-++-++-++-++-+ | | | | | +-- Unused | | | | +----- Auto Spin Start | | | +-------- Slave Sync | | +----------- External Activity LED | +-------------- Ground +----------------- Write Protect The 68Pin models contain an Auxiliary connector that replicates some of the functions contained in the Front Option Jumper Block. The Auxiliary connector signal definitions conforms to the SCSI document SFF-8009 Rev. 2 with the following exceptions: 1. EXTERNAL FAULT (XTFALT-) is not supported on pin 2. 2. AUTO SPIN START was chosen as the vendor unique'signal assignment (on pin 4). (This signal is an input to the drive. The SCSI spec (SCSI SFF-8009) specifies this pin as an output.) This signal should be useful for those applications that want to auto-start the drive based on location dependent SCSI ID. This pin should be handled in one of the following ways: a. tied to ground (auto spin start enabled) b. allowed to float (no connection) c. drive with an open collector driver (>1mA sink capability) 50-Pin SCSI ID -------------- +----------+-----------------------+ | SCSI ID | MSB LSB | | | Bit 2 | Bit 1 | Bit 0 | +----------+-------+-------+-------+ | 0 | OPEN | OPEN | OPEN | +----------+-------+-------+-------+ | 1 | OPEN | OPEN | CLOSED| +----------+-------+-------+-------+ | 2 | OPEN | CLOSED| OPEN | +----------+-------+-------+-------+ | 3 | OPEN | CLOSED| CLOSED| +----------+-------+-------+-------+ | 4 | CLOSED| OPEN | OPEN | +----------+-------+-------+-------+ | 5 | CLOSED| OPEN | CLOSED| +----------+-------+-------+-------+ | 6 | CLOSED| CLOSED| OPEN | +----------+-------+-------+-------+ | 7 | CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+ 68-Pin SCSI ID -------------- +----------+-------------------------------+ | SCSI ID | Jumper Location | | | PINS | | | Bit 3 | Bit 2 | Bit 1 | Bit 0 | +----------+-------+-------+-------+-------+ | 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| +----------+-------+-------+-------+-------+ Auto Start (& Delay) Pins ------------------------- The Auto Start and Auto Start Delay pins control when and how the drive can spin up and come ready. When configured for Auto-Startup, the motor spins up after power is applied without the need of a SCSI Start Unit command. For no Auto-Start, a SCSI Start Unit command is required to make the drive spin and be ready for media access operations. When in Auto-Start mode, the drive will delay it's start time by a period of time multiplied by it's own SCSI address. Pins (50 and 68 interface pin models) +----------+----------+----------+-----+ |Auto Start|Auto Start|Auto-Start|Delay| |Delay | |Mode ? |(sec)| +----------+----------+----------+-----+ |OPEN |OPEN |NO | NA | +----------+----------+----------+-----+ |OPEN |CLOSED |YES | 0 | +----------+----------+----------+-----+ |CLOSED |OPEN |YES | 10 | +----------+----------+----------+-----+ |CLOSED |CLOSED |YES | 4 | +----------+----------+----------+-----+ Auto-Startup Modes selectable by Auto-Start/Delay Pin Combinations Pins (80 interface pin models) +----------+----------+----------+-----+ |Auto Start|Auto Start|Auto-Start|Delay| |Delay | |Mode ? |(sec)| +----------+----------+----------+-----+ |OPEN |OPEN |YES | 0 | +----------+----------+----------+-----+ |OPEN |CLOSED |NO | N/A | +----------+----------+----------+-----+ |CLOSED |OPEN |YES | 10 | +----------+----------+----------+-----+ |CLOSED |CLOSED |NO | N/A | +----------+----------+----------+-----+ Auto-Startup Modes selectable by Auto-Start/Delay Pin Combinations External Activity (LED) Pins ---------------------------- The LED pins can be used to drive an external Light Emitting Diode. Up to 33 mA ( 5%) of TTL level LED drive capability is provided. Current limiting for the LED is provided on the electronic card. The LED Anode may be tied to the +5V source provided on pin 18 of the Front Option Jumper block, pin 11 of the Auxiliary connector on the 68-pin. Unitized connector or the +5V power source provided on the 80-pin SCA model. The LED cathode is then connected to the EXTERNAL ACTIVITY Pin to complete the circuit. NOTE This set of pins can be used to drive an LED located in a bezel connected to the front of the drive or to an external LED in systems where the front of the drive can not be easily seen. NOTE 68/80 pin SCSI models have two sets of pins, a set on the front and a set on the back, that are connected to the same LED driver circuit. The combined drive capability is stated above. Write Protect Pins ------------------ If the Write Protect pin is jumpered to ground the drive will prohibit SCSI commands that alter the customer data area portion of the media from being performed. The state of this pin is monitored on a per command basis. Disable T.I.Sync. Negotiation Pins ---------------------------------- If a Disable Target Initiated Synchronous Negotiation pin is grounded then an Initiator is required to start a negotiation handshake if Synchronous and/or Wide (Double Byte) SCSI transfers are desired. Disable SCSI Parity Pins ------------------------ Grounding this pin will disable SCSI Parity checking. Disable Unit Attention Pins --------------------------- Grounding this pin will disable the drive from building Unit Attention Sense information for commands immediately following a Power On Reset (POR) or SCSI Bus Reset. Any pending Unit Attention conditions will also be cleared at POR or SCSI Reset times. Customizing Pin --------------- The customizing pin is currently reserved for future use. Enable Narrow Mode ------------------ Jumpering pin 14 to pin 13 will cause the 68 pin Differential or the 80 pin SCA to operate in a Single Byte mode. The drive will not negotiate for Wide (Double Byte) operation. The drive will terminate the unused upper byte and upper byte parity on the SCSI Bus. Enable Active Termination ------------------------- Upon request, Single Ended 50 and 68 pin models are available with on card SCSI bus Active terminators. For those cards having the Active Termination feature, this function can be enabled by installing a jumper between pins 13 and 14 of the Front Option Jumper Block or connecting pins 9 and 11 of the Auxiliary Connector on 68 SCSI pin models. SCSI Bus Termination Power -------------------------- Termination Power is optionally provided for systems that desire to use it. In order to use the termination power, the user needs to install a jumper between pins 01 and 02 of the TermPower Block. The jumper should only be installed on one device, which should be the last device on the SCSI bus (i.e. the drive that is phydically closest to a terminator). 68 pin models can source up to 2.0 Amps of current at 5.0 Volts ( 5%) for termination power. 50 pin models can source up to 1.5 Amps of current at 5.0 Volts ( 5%) for termination power. ********************************************************************** I N S T A L L ********************************************************************** IBM DFHS-S1X/S2X/S4X ULTRASTAR XP PRODUCT DESCRIPTION Notes on Installation ===================== Installation direction ---------------------- horizontally vertically +-----------------+ +--+ +--+ | | | +-----+ +-----+ | | | | | | | | | +-+-----------------+-+ | | | | | | +---------------------+ | | | | | | | | | | | | | | | | | | +---------------------+ | +-----+ +-----+ | +-+-----------------+-+ +--+ +--+ | | | | +-----------------+ The drive will operate in all axis (6 directions). Mounting -------- The drive can be mounted with any surface facing down. The drive has both side and bottom mounting holes. The maximum allowable penetration of the mounting screws is 3.8 mm. The torque applied to the mounting screws must be 0.8 Newton-meters 0.1 Newton-meters. Clearances ---------- A minimum of 2 mm clearance should be given to the bottom surface except for a 10mm diameter area around the bottom mounting holes. For proper cooling it is suggested that a clearance of 6 mm be provided under the file and on top of the file. NOTE The top of the drive will not exceed the height dimensions by more than 2 millimeters during a non-operating shock. Power Connector --------------- The DC power connector used on all models (50, 68 and 80 pin SCA) are an integral portion of the 50/68 pin SCSI Unitized Connectors or the 80 pin Single Connector Attachment (SCA) Connector. +------------+ pin 1 +12 VDC | 4 3 2 1 | pin 2 +12 Volts Return +------------+ pin 3 + 5 Volts Return pin 4 + 5 VDC 50-Pin SCSI Bus Connector ------------------------- 50-pin models use an AMP PN 84160-1. The connector is compatible with the ANSI SCSI "A" connector specifications. It is limited to 8 bit data transfers only. 68-Pin SCSI Bus Connector ------------------------- 68-pin models use an AMP 786963-1 that is compatible with the ANSI SCSI "P" connector specifications. It can transfer data in both 8 bit (narrow) and 16 bit (wide) modes. NOTE Note that the "P" connector is not mechanically compatible with the 50-pin "A" connector as defined in the ANSI SCSI-2 standard. Therefore system cables used with 50 pin products cannot be plugged directly into the 68 pin models. Despite the difference in connector, the differential 68-pin models are electrically compatible with differential 50-pin models and other 50-pin differential SCSI products and therefore can coexist on the same bus. In order to do so, the differences in connector types would need to be accounted for in the cable. The same can be said for connecting 68 and 50 pin single-ended models to the same bus. 80 Pin SCA (Single Connector Attachment) Connector -------------------------------------------------- 80 pin SCA models use a Molex connector (PN 87091-0001) that is compatible with the specification of Single Connector Attachment for Small SCSI Disk Drives. It can transfer data in both 8 bit (narrow) and 16 bit (wide) modes. NOTE That the SCA connector is not mechanically compaible with the 50 pin A connector or the 68 pin P connector as defined in the ANSI SCSI standard. This connector is intended for direct backplane attachment and is not intended to be cable attched to the bus. SCSI Bus Cable -------------- Single-ended models permit cable length of up to 6 meters (19.68 feet). It should be noted however that users who plan to use "Fast" data transfers with single-ended models should follow all of the SCSI-3 guidelines for single-ended "Fast" operations. This may include a cable length of less than 6 meters. SCA connector models are not designed for direct cable attachment due to the combination of power and SCSI bus signals. Fast data transfers with SCA models should follow of the ANSI SCSI guidelines for single ended Fast operations. Differential models permit cable length of up to 25 meters (82.02 feet). Cables must meet the requirements for differential cables as set forth in the ANSI SCSI-2 standard under "Cable Requirements - Differential Cable". The ANSI SCSI standard states that any stub from main cable must not exceed 0.1 meters for single-ended cables and 0.2 meters for differential cables. DFHS has a maximum internal stub length of 0.03 meters on all single-ended, and 0.1 meters on all differential SCSI signals. To remain compliant with the standard, the SCSI bus cable must not add more than 0.05 meters additional stub length to any of the single-ended SCSI signals or 0.1 meters to any differential SCSI signals. SCSI Bus Terminators (Optional) ------------------------------- For those cards having the Active Termination feature this function can be enabled by installing a jumper between pins 13 and 14 of the Front Options Jumper Block or pins 9 and 11 of the Rear Block on 68 pin models. The using system is responsible for making sure that all required signals are terminated at both ends of the cable. 80 pin SCA models do not have internal SCSI bus terminators. Some external terminator possibilities for single-ended cables systems are listed in the following Table. +-------------------------+-------------------------+ |50 Pin Model Terminators | 68 Pin Model Terminators| +-------------------------+-------------------------+ |Data Mate DM550-06-0 | Data Mate DM5000 68689 | +-------------------------+-------------------------+ |Data Mate DM1050-02-0 | Data Mate DM2050-02-685 | +-------------------------+-------------------------+ Differential models do not have internal SCSI bus terminators. Some terminator possibilities are listed in the following Table. +-------------------------+-------------------------+ |50 Pin Model Terminators | 68 Pin Model Terminators| +-------------------------+-------------------------+ |Data Mate DM550-05-0 | Data Mate DM2050-01-68D | |Data Mate DM1050-06-0 | Data Mate DM5000 686810 | +-------------------------+-------------------------+ NOTE A Meritec model 940900-4 or a DataMate DM5000-5068-11 can be used to connect the 68 pin connector on a SxW drive for use with a 50 pin connector. The drive will now perform 8 bit transfers. Recommendations For SCSI Bus Noise Reduction -------------------------------------------- The SCSI commitee has spent a large amount of resource looking into what needs to be done to assure SCSI devices will work as specified in the SCSI-2 standard. As a result of this, the committee is recommending the following approach: 1. Use the regulated 110 ohm terminator 2. Use AWG 28 polyolefin shielded cables 3. Make sure data and parity are on the outer ring of the cable and that REQ and ACK are in the core of the cable. Spindle Synchronization Oberview -------------------------------- There are four modes of spindle synchronization. The following paragraphs give a short description of each spindle synchronization mode: - The Slave drive (Slave Sync mode) receives the index from the Master drive on the -SLAVE SYNC line and synchronizes its INDEX (Slave index) to it. - Should the drive be the Master drive, (Master Sync mode), it out- puts its INDEX on the -MASTER SYNC and the -SLAVE SYNC lines. The Master drive does not synchronize its index to any other device. It simply outputs its INDEX. - In the Master Sync Control mode, a drive will synchronize its spindle to the signal it receives on the -SLAVE SYNC input. It out- puts to -MASTER SYNC a pulse that has the same period as the drive INDEX, but is not synchronized to the drive INDEX generated from the disk. - In the non-sync mode, the drive will receive the -Slave SYNC signal, but it is not used by the drive. Spindle Synchronization Control Lines +------------+-----------+-------------------+ |-MASTER SYNC|-SLAVE SYNC|function mode | +------------+-----------+-------------------+ |released |receive |Slave sync | +------------+-----------+-------------------+ |drive |drive |Master sync | +------------+-----------+-------------------+ |drive |receive |Master Sync Control| +------------+-----------+-------------------+ |released |receive |non sync | +------------+-----------+-------------------+ - File Synchronization with Offset The file electronics receives the Master Index and creates the delayed Slave Index from the drive INDEX. The delay is determined by using the Mode select command, Rigid Disk Drive Geometry Parameters (page 4). A rotational offset of 0/256 of a revolution up to 255/256 of a revolution may be selected in increments of 1/ 256 of a revolution. - Synchronization Time The SCSI MODE Slect command is used to select the Spindle Sync. mode. It could take up to 3 seconds (1.5 sec. nominally) to synchronize the Slave drive to the Master drive. While the Slave drive is synchronizing to the Master, it will not be able to read and write data. Once synchronized, the drive will maintain 20 usec synchronization tolerance. Spindle Synchronization Bus --------------------------- The spindle synchronization Bus consists of the two signal lines, -MASTER SYNC and -SLAVE SYNC. - Termination Bus termination of the -MASTER SYNC and -SLAVE SYNC signals is internal to the file. These two signals each have a 2000 ohm pullup to the +5 volt supply. A maximum of 16 files can have their -MASTER SYNC or -SLAVE SYNC lines daisy chained together. Violating this could damage the Master file driver on the -MASTER SYNC and/or -SLAVE SYNC line. - Bus Characteristics - maximum Bus length = 6 meters - 1 micro-seconds negative active pulse - 0.8 volts = valid low input - 2.2 volts = valid high input - 0.4 volts = low output _ Vcc volts = high output - 60 milli-amps = maximum output low level sink current The driver used for these two signal lines is an open collector buffer. Hot plug/unplug support ----------------------- Power supply and SCSI bus hot plug and un-plug is allowed. There is no special sequence required for connecting 5 volts, 12 volts, or ground. During a hot plug-in event the file being plugged will draw a large amount of current at the instant of plug-in. This current spike is due to charging the bypass capacitors on the file. This current pulse may cause the power supply to go out of regulation. If this supply is shared by other files then a low voltage power on reset may be initiated on those files. Therefore the recommendation for hot plugging is to have one supply for each file. Never daisy chain the power leads if hot plugging is planned. Hot plugging should be minimized to prevent wear on the power connector. Hot plugging the SCSI bus may cause glitches on the bus. To minimize the chance of glitching, it is recommended to plug in the SCSI bus before the power is applied. During hot plugging, the supplies must not go over the upper voltage limit. This means that proper ESD protection must be used during the plugging event. ********************************************************************** F E A T U R E S ********************************************************************** IBM DFHS-S1X/S2X/S4X ULTRASTAR XP PRODUCT DESCRIPTION Features -------- - Industry-standard interface: ANSI/SCSI-2, single-ended 68 pin ANSI SCSI-3, single-ended/differential 80 pin SCA - Magnetoresistive (MR) heads - PRML data channel - read-ahead caching - No preventative maintenance required - Spindle synchronization - Write cache supported - ECC on the fly SCSI Bus Termination Power Short Circuit Protection --------------------------------------------------- The ANSI SCSI-2 specification recommends for devices that optionally supply TERMPWR, to include current limiting protection for accidental short circuits. It also recommends that the maximum current available for TERMPWR should not exceed 5 Amps. UL has a different requirement that they call the 8 Amp rule. This rule states that when a power source leaves an enclosure (like SCSI TERMPWR in the SCSI cable), it must trip 8 Amps of current within 1 minute. The drive limits current to 5.0 amps through the use of a permanent fuse mounted on the electronics card. Systems may also provide short circuit protection for drive supplied TERMPWR by limiting the current of the 5V power is supplies to the drive. Grounding Requirements of the Disk Enclosure -------------------------------------------- The disk enclosure is at Power Supply ground potential. It is allowable for the user mounting scheme to common the Disk Enclosure to Frame Ground potential or leave it isolated from Frame Ground. The drive's mounting frame must be within 150 millivolts of the drive's power supply ground. At no time should more than 35 milliamps of current (0 to 100 Mhz) be injected into the disk enclosure.