RISC DISC 2

home *** CD-ROM | disk | FTP | other *** search

/ RISC DISC 2 / RISC_DISC_2.iso / pd_share / program / code / andylib / Notes / SCSIDriver next >

Wrap

Text File | 1991-06-28 | 31.7 KB | 956 lines

RISC OS SCSIdriver ================== Author: Nick Reeves, Richard Manby, BC Version: 0.18 History 1) 24-Nov-88 NR: Initial draft 2) 02-Dec-88 NR: Added a) timeout parameter for SCSI_Op b) SCSI_Op to return operation id number, which can be used to abort operation. c) parameter for number of bytes of extended sense 0.03: 31-Jan-89 RCM: Copy placed in Arf:doc 0.04: 1-Mar-89 RCM: Defined data returned by 'Determine Device' 0.05: 15-Mar-89 RCM: Removed 'Establish Device' and 'Remove Device' reason codes from SWI SCSI_Initialise. Changed reason codes for 'Determine Device' in SWI SCSI_Initialise from 4 to 2. Removed 'Return error statistics' from SWI SCSI_Status. SWI SCSI_Op; Moved transfer direction, Scatter, Poll, Retry & Background Bits in R0 into MSByte to leave room for its device ID field to grow. Added 'Set Error Response','Set Queue Behaviour' & 'Disconnect' to SWI SCSI_Control. 0.06: 17-Apr-89 RCM: Removed the scatter list Bit from SWI SCSI_Op, this Bit is now reserved. Commands execute totaly in the foreground or in the background. The 'return-after-some-of-the-data-has- been-transfered' cannot be supported by SCSI. Added section on error messages. 0.07: 25-Apr-89 RCM: Tidied up some of the error messages Full definition of Host ID and Device ID 0.08: 16-May-89 RCM: Reordered reason codes for SCSI_Control-SetErrorResponse. SetErrorResponse, SetTimeout & ControlDisconnect now return their previous settings. 0.09: 08-Jun-89 BC+RCM: Changed spec of SCSI_Version to indicate the hardware and software types as a Bitset. Added all the error messages and their numbers, documented *Devices. Admitted to total reentrancy and interrupt kosherness. Scatter list reimplemented. 0.10: 26-Jun-89 RCM: Removed restrictions on device having to be idle before issuing SWI SCSI_Control (eg on SetTimeout). Defined bit value for 'supports scatterlist' and for 'supports device reservation'. Added SWI SCSI_Reserve. Added R8 (access key) to any dangerous operations. 0.11: 30-Jun-89 RCM: Reordered the error message section, so it made more sense. Added recommendations to SCSI_Control about the use of the control_disconnect reason code. 0.12: 04-Jul-89 RCM: Changed "Device reserved" to "Reservation error" 0.13: 12-Jul-89 RCM: Added SWI SCSI_List, *ScsiBlock 0.14: 23-Aug-89 RCM: Added accesskey to *ScsiBlock 0.15: 29-Aug-89 RCM: Added reason code 3 to SWI SCSI_Initialise. 0.16: 04-Sep-89 RCM: Changed "Reservation error" to "SCSI driver reservation error" 0.17: 19-Oct-89 RCM: Reset Bus restores various defaults. 0.18: 20-Oct-89 RCM: Added SBIC bug warning. ============================================ INTERFACE FOR THE RISC OS SCSI DEVICE DRIVER ============================================ Introduction ============ The SCSI device driver for RISC OS is a relocatable module whose interface consists of the following SWIs: SCSI_Version 403C0 603C0 SCSI_Initialise 403C1 603C1 SCSI_Control 403C2 603C2 SCSI_Op 403C3 603C3 SCSI_Status 403C4 603C4 SCSI_ReadControlLines 403C5 603C5 SCSI_EEProm 403C6 603C6 SCSI_Reserve 403C7 603C7 SCSI_List 403C8 603C8 and the following * commands: *Devices *ScsiBlock (N.B. NOT IMPLEMENTED BY ACORN SCSIdriver) Note on Device ID and Host ID ----------------------------- The device ID is a composite of the SCSI id number, the logical unit number (LUN) within the device and the logical slot number of the SCSI card. They are packed into 8 bits as follows: Bits 2..0 SCSI device id (0..7) Bits 4..3 Logical SCSI card number (0..3) Bits 7..5 Logical unit number (0..7) The SCSI card numbering is based on the relative slot positions of any SCSI cards in the machine, thus in a machine with 2 cards, in physical slots 2 and 4 they are refered to as logical SCSI card numbers 0 and 1. In a machine with 1 card it may be placed in any slot refered to as logical SCSI card number 0. The host ID is a similar composite, but of SCSI id number and logical slot number, with no LUN field. Bits 2..0 Host device id (0..7) - Usually 7 Bits 4..3 Logical SCSI card number (0..3) The Host device id is usually 7 and there must be no other devices on the bus with the same id. The SWIs ======== All SWIs conform to the RISC OS standard that is a) Any registers not explicitly defined as result parameters are preserved b) The processor flags N,Z and C are preserved. c) Errors are indicated by setting V and returning with R0 pointing at an error block (If the Bit 17 clear version is called control passes to the error handler instead). d) All SWIs preserve the interrupt state unless stated otherwise, and so they may be called from interrupt or event routines. e) All SWIs are reentrant. ---------------------------------------------------------------------------- SCSI_Version (403C0 & 603C0) ============ This SWI is used to determine the version number of the drivers, whether it supports any particular later extension, and what particular hardware implementation is present. entry: no parameters exit: R0 Bits 0..7 software minor version number, 0 for any release Bits 8..31 software major version number eg 100 for 1.00 R1 Bitset of software features R2 Bits 0..7 hardware minor version number, 0 for any release Bits 8..31 hardware major version number eg 100 for 1.00 R3 Bitset of hardware features The Bitset of software features is defined as follows; Bit 31 Supports target mode Bit 30 Supports configuration Bit 29 Supports reading control lines Bit 28 Supports device reservation Bit 27 Supports multiple SCSI cards (and hence SWI SCSI_List) Bit 26 Supports *ScsiBlock Bits 25..16 Reserved must be 0 Bits 15..7 Reserved must be 1 Bit 6 Supports *Devices Bit 5 Supports scatter list for SWI SCSI_Op Bit 4 Supports messaging Bit 3 Supports automatic "Request Sense" Bit 2 Supports command queueing Bit 1 Supports background data transfer Bit 0 Supports target disconnect/reconnect The Bitset of hardware features is defined as follows; Bit 31 Supports configuration Bits 30..16 Reserved must be 0 Bits 15..1 Reserved must be 1 Bit 0 Supports target mode errors: none --------------------------------------------------------------------------- SCSI_Initialise (403C1 & 603C1) =============== This SWI performs various initialisations determined by a reason code in R0. Any additional parameters are given in subsequent registers. 'Reset Bus' ----------- entry: R0 0 R1 host ID This call resets all options set by SCSI_Control to their default states and removes any device reservations. In addition it sets a new host ID and causes a full reset of the SCSI bus by driving the SCSI bus RESET line. The default states set for each device are Reservation - none Timeout=0 - no timeout Error response - report check condition as an error Queue behaviour - wait until slot becomes free Disconnect - allow disconnect/reselect success exit: no results errors: &00020100 - No room for SCSI driver workspace &00020103 - SCSI bus failed to reset &00020104 - Invalid SCSI host ID 'Reset Device' - initiates the reset operation and returns immediately. -------------- entry: R0 1 R1 device ID R8 access key success exit: no results errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'Determine Device' - performs an Inquiry command to see what type the device ------------------ is and then performs the appropriate Read-Capacity command depending on the device type. entry: R0 2 R1 device ID R2 pointer to buffer for description, (16 bytes, word aligned). success exit: buffer filled in Offset R2 --> 0 Type = &00 Direct-access (eg magnetic disk) &01 Sequential-access (eg magnetic tape) &02 Printer device &03 Processor device &04 Write-once read-multiple (eg some optical discs) &05 Read-only (eg some optical discs) &06-7E Reserved &7F Logical unit not present &80-FF Vendor unique 1 Removable medium Bit (Bit7)/Device-Type Qualifier (Bits 0..6) 2 ISO (b7..6)/ECMA (b5..3)/ANSI (b2..0) version 3 Reserved (reserved field returned by inquiry command) 4 Additional length, extra data that could be obtained by an inquiry command 5 } 6 } Reserved (by device driver - currently zero) 7 } 8..11 word highest logical block number (converted to normal) 12..15 word block length ( ARM byte sex) errors: &00020105 - Invalid SCSI device ID &0002010A - Timeout Bytes 0..4 are the first 5 bytes returned by an inquiry command, byte 5 is provided to indicate how much additional data (vendor ID,product ID etc) could be obtained by an Inquiry command Bytes 5..7 are reserved by the device driver Bytes 8..11 (word 2) & 12..15 (word 3) are the highest block count and block size returned by a Read Capacity command but have had the byte sex reversed to suit ARM's LDR instruction. 'Enumerate Device' - performs an Inquiry command to see what type the device ------------------ is and then performs the appropriate Read-Capacity Data returned as formatted text. entry: R0 3 R1 device ID R2 pointer to buffer for description, word aligned). R3 buffer size The data returned is a zero terminated string of the same form as that printed by *devices, ie "ddd ttttttttttttttttt cccc Mbytes vvvvvvvv pppppppppppppppp rrrr" where the fields are device number, type, capacity, vendor, product and revision number. If a device doesn't respond, a string containing just the device number is returned, if the device responds, but the 'read-capacity' call fails, the capacity field will be set to unknown. ---------------------------------------------------------------------------- SCSI_Control (403C2 & 603C2) ============ This SWI issuess various control commands determined by a reason code in R0. Any additional parameters are given in subsequent registers. 'Abort device' - cancels all outstanding operations on a device. 'Abort op' -------------- should normally be used instead wherever possible. entry: R0 0 R1 device ID R8 access key success exit: no results errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'Abort op' - cancels a particular operation on a device. ---------- entry: R0 1 R1 device ID R2 operation id as returned by SCSI_Op R8 access key success exit: no results errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error Reserved -------- entry: R0 2 R8 access key 'Set Timeout' - sets the default timeout for a device. ------------- entry: R0 3 R1 device ID R2 timeout value in centi-seconds or zero for no timeout R8 access key exit: R2 previous timeout setting errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'Set Error Response' - controls the behaviour of CHECK CONDITION status. -------------------- entry: R0 4 R1 device ID R2 0 If device returns 'check condition', return that as an error message. This is for badly behaved devices with non-standard request sense return blocks. 1 If device returns 'check condition' do a request sense automaticaly, report the error. 2 If device returns 'check condition' do a request sense automaticaly, if 'unit attention', ignore it and reissue the command else report the error. -1 no action, return previous setting. R8 access key exit: R2 previous setting errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'Set Queue Behaviour' --------------------- The driver supports disconnection/reselection and queueing of commands, this implies that when a command is issued, the podule hardware may be in use servicing another command, a command maybe queued/running for the target device or the queue may be full. entry: R0 5 R1 device ID R2 0 ie if queue full loop until a slot becomes free if command operates totally in the background control returns to the caller as soon as the command is queued if the command operates in the forground, portion, control returns when the command completes. 1 Reject if queue full ie command accepted only if it can be queued/run without waiting. if command operates totally in background, control returns to the caller as soon as the command is queued if the command operates in the forground, portion, control returns when the command completes. 2 Reject if device busy ie command accepted only there are no other (or queue full) queued/running for this device. 3 Reject if podule busy ie accept command only if it will run immediatly -1 no action, return previous setting. R8 access key exit: R2 previous setting errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'Disconnect' - Allow/Inhibit disconnect/reselect ------------ entry: R0 6 R1 device ID R2 0 allow disconnect/reselect (ie when the bus selection phase is complete, the driver will attempt to send an IDENTIFY message with bit6 set, this tells the target that it may disconnect if it wants to). 1 inhibit disconnect/reselect, so that once started, a command will proceed to completion without allowing any other command to start/reconnect. (ie when the bus selection phase is complete the driver will attempt to send an IDENTIFY message with bit6 clear). 2 inhibit disconnect/reselect by not sending an identify message -1 no action, return previous setting. R8 access key exit: R2 previous setting errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error Note codes 0/1 cause SWI SCSI_Op to attempt to send an identify message once the bus selection phase is complete. The target may choose not to take the message (Not an error), in which case the driver proceedes to the command phase. The target may reply to the message with a message reject. These two cases do not produce an error from SCSI_Op, as the command may still complete successfully, it will however remain connected all the time. Note Applications/filing systems are NOT expected to issue this call, as all software/hardware should work happily regardless of any disconnections that occur. It should only be issued by: 1) The user (in his/her boot file) if his/her particular device mis-behaves when sent messages. 2) Application/filing system software specific to one vendors product that is known to mis-behave when sent messages. ---------------------------------------------------------------------------- SCSI_Op (403C3 & 603C3) - issues a SCSI command to a device. ======= Can be called in the background. R0 Bits 0..7 Device ID Bits 24..25 00 => no data transfer, 01 => read, 10=>write, 11=>reserved Bit 26 Scatter Bit, if set, R3 is a pointer to a scatter list. Bit 27 If clear, poll escape during transfer and abort if escape pressed Bit 28 If set, repeatedly retry on timeout Bit 29 Set if a background transfer (possibly 0 length). R1 Length of SCSI control block R2 Ptr to SCSI control block R3 RAM ptr for start of transfer or pointer to scatter list of address length pairs if Bit 26 of R0 is set. After each chunk in the scatter list is transferred the address should be incremented and the length set to 0. R4 Length of transfer (in bytes). R5 Timeout in centiseconds or 0 for default timeout R6 Address to call back when transfer is complete if background Bit set. The call is made in IRQ mode with IRQs disabled. If an error has occurred, V is set, R0 points to a non-dynamic error block, (ie a pointer to a fixed block in the module rather than built up in a buffer), R1 indicates the cause of the error and R2 the logical address on the device of where the error occured. R7 Workspace pointer to pass in R12 for background call back. R8 access key exit (V clear) R0 returns a 32 Bit id incremented for each operation. Used to cancel op. R3 updated to indicate how much of transfer was successful (if scatter list, pointer to first unused/partially used entry). R4 updated to the amount untransferred exit (V set) R0 points to an error block R1 indicates the cause of the error R2 hold the logical address on the device of where the error occured. R3 updated to indicate how much of transfer was successful (if scatter list, points to first unused entry, entry is updated to indicate amount transfered). R4 updated to the amount untransferred errors: many Interrupts may be enabled by the call, this does not affect it's reentrancy. N.B. See below for detailed description of errors ---------------------------------------------------------------------------- SCSI_Status (403C4 & 603C4) =========== This SWI issues various control commands determined by a reason code in R0. Any additional parameters are given in subsequent registers. 'Check Device Status' - returns the status of the selected device --------------------- entry: R0 0 R1 device ID success exit: R0 status 1 => Idle 2 => Busy 4 => Error 16 => not available errors: &00020105 - Invalid SCSI device ID ---------------------------------------------------------------------------- SCSI_ReadControlLines (403C5 & 603C5) N.B. NOT IMPLEMENTED BY ACORN SCSIdriver ===================== Returns current state of SCSI bus lines entry: R0 host ID success exit: R0 SCSI data bus R1 Control lines, 1 = asserted : Bit 7 6 5 4 3 2 1 0 RST BSY REQ MSG C/D I/O SEL DBP R2 Control lines, 1 = asserted : Bit 7 6 5 4 3 2 1 0 ATN ACK (Bits 7..2 are Bits of 5380 bus & status register) errors: &00020104 - Invalid SCSI host ID ---------------------------------------------------------------------------- SCSI_EEProm (403C6 & 603C6) N.B. NOT IMPLEMENTED BY ACORN SCSIdriver =========== Reads/writes EEProm on SCSI podule entry: R0 Bits 0..3 address of 16 Bit word Bit 10 set for write, clear for read R1 Bits 0..15 write data (if R0 Bit 10 set) success exit: R0 data read if R0 Bit 10 was set on entry R0 preserved if R0 Bit 10 was clear on entry errors: ---------------------------------------------------------------------------- SCSI_Reserve (403C7 & 603C7) ============ This SWI allows the caller to claim exclusive use of a device and may prevent data corruption problems that may arise if a program (by accident or on purpose) issues a Write/Format/ModeSelect command to a device currently mounted by SCSIFS. It also provides for a clean change of device ownership from one user to another, as SCSIdm for example is entitled to modify your disc, (to map out defects/format/partition it etc) but must only do so once SCSIFS has closed down all open files and dismounted the disc. 'Claim' - Claim exclusive use of a device ------- This call attempts to claim exclusive use of the given device. If the call is successful, the caller will be granted sole use of the 'dangerous' SCSIdriver calls for that device and may use them itself, only by supplying the access key registered at 'Claim' time. Other callers may only use safe calls such as SCSI_Initialise-DetermineDevice. If the device has already been claimed, an error message 'SCSI driver reservation error' will be returned. entry R0 0 R1 device ID R2 release address R3 workspace pointer, to be passed in R12 when release address is called R8 access key exit VC VS & R0-> error errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error 'ForceClaim' ------------ This call is similar to 'Claim' above, however, if the device is already claimed, it will ask the current claimant to release it, by calling the release address registered for that device. The current owner should try to tidy up, and call 'Release' but may refuse by returning VS and R0 pointing to an error message Aside: This call is used by SCSIdm to ask SCSIfs to close files and dismount etc entry R0 1 R1 device ID R2 release address R3 workspace pointer, to be passed in R12 when release address is called R8 access key exit VC VS & R0-> error errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error OR an error message passed back by the current claimant. When the current claimant is called R0 will hold a reason code indicating: R0 = 1 called from ForceClaim 'Release' --------- This call will remove the reservation of a device. entry R0 2 R1 device ID R8 access key (to prove you actually claimed it) exit VC VS -> error errors: &00020105 - Invalid SCSI device ID &0002010E - SCSI driver reservation error Passing access key value to SCSI SWI's ====================================== The access key (probably WorkSpacePointer) should be passed in R8 and is only checked if the specified device is claimed and the call/reason code is 'dangerous'. ---------------------------------------------------------------------------- SCSI_List (403C8 & 603C8) ========= This is used by the ScsiLog module as part of the multiple SCSI card initialisation sequence (see separate SCSILog documentation). exit: R0 -> Null terminated list of podule addresses This SWI returns a pointer to a null terminated list of SCSI podules available to SCSIdriver. The addresses are those of the 'slow access' space for the podule, ie, &03240000, &03244000, &03248000 or &0324C000 for podule slot 0,1,2 or 3. ---------------------------------------------------------------------------- SCSI messages & error codes =========================== Errors reported by the SCSIdriver fall into 3 classes: 1) Those generated/detected by the driver 2) Interpretations of the SCSI status byte returned on command completion. 3) Interpretation of the sense data (collected on CHECK CONDITION status if the error response is set to 0 or 1). Device driver errors ==================== &00020100 = "No room for SCSI driver workspace" &00020101 = "Unknown SCSI SWI number" &00020102 = "Unknown reason code for SCSI SWI" &00020103 = "SCSI bus failed to reset &00020104 = "Invalid SCSI host ID" &00020105 = "Invalid SCSI device ID &00020109 = "Device not idle" &0002010A = "Timeout" ; During selection phase &0002010B = "Timeout" ; During any other phase &0002010C = "Command queue not empty" &0002010D = "Command queue full" &0002010E = "SCSI driver reservation error" &0002010F = "Invalid parameters" &00020110 = "Parameter error" &00020111 = "Not callable from IRQ routine" (reported by podule loader) &00020112 = "Operation aborted" &00020113 = "Unexpected disconnection" Interpretation of the returned SCSI status byte =============================================== On completion of the command, the target returns a status byte. The Vendor unique Bits are masked out and the following interpretations placed on the result. If the returned status is GOOD then that is not an error so there will not be an error returned. If the status retured is not GOOD then it will be translated into one of the following three errors; &00020180 = "Target status - Check condition" &00020181 = "Target status - Busy" &00020182 = "Target status - Unknown" Any other value, including GOOD/CHECK CONDITION/BUSY with reserved Bit 7 set, is reported as an error "Target status - Unknown" If the error response level is 1 or 2, then on 'CHECK CONDITION', the driver will automatically perform a request sense. Interpretation of the Sense data ================================ The first byte of returned sense data is masked to leave the Error-class/error-code code Bits these are interpreted as: 0x..6x vendor unique error (non extended sense) } Reported as 71..7E reserved error (extended sense) } "Target error - Unknown" 7F vendor unique error (extended sense) } 70 (extended sense), the error is given by examination of the 'sense key' in byte 2 of the sense data &000201C0 = "Target error - No sense" &000201C1 = "Target error - Recovered error" &000201C2 = "Target error - Not ready" &000201C3 = "Target error - Medium error" &000201C4 = "Target error - Hardware error" &000201C5 = "Target error - Illegal request" &000201C6 = "Target error - Unit attention" &000201C7 = "Target error - Data protect" &000201C8 = "Target error - Blank check" &000201C9 = "Target error - Vendor unique" &000201CA = "Target error - Copy aborted" &000201CB = "Target error - Aborted command" &000201CC = "Target error - Equal" &000201CD = "Target error - Volume overflow" &000201CE = "Target error - Miscompare" &000201CF = "Target error - Reserved sense key" &000201D0 = "Target error - Unknown" Errors produced by calling SWI SCSI_Op ====================================== When an error is returned by a call of SWI SCSI_Op, in addition to the normal error pointer in R0, R1 and R2 provide extra information: R0 -> error message - a standard RISC OS error block, consisting of a 1 word error number, followed by an error message R1 = error indication - this is a composite of the LSB of the above error number and the status/sense-errorclass/sense key that produced the error. R2 = logical address on the device of where the error occured. Device driver detected errors ============================= R1 MSB = the LSB of the RISC OS error number. ie 0..127 R1 = 0 (see note below) R1 = TBA } If error was due to an unexpected bus phase, the phase could R1 LSB = TBA } be indicated here - assume undefined for now. R2 = undefined R3 = undefined R4 = undefined Status byte errors ================== R1 MSB = the LSB of the RISC OS error number. ie 128..195 R1 = 0 (see note below) R1 = 0 R1 LSB = returned status byte (unmasked) R2 = undefined R3 = indicates amount of data transfered R4 = amount of data not transfered Returned Sense data =================== Non-extended sense data returned -------------------------------- R1 MSB = the LSB of the RISC OS error number. ie 196..255 R1 UMB = Bits 23..16 holds byte 0 of the returned sense data Bit 23 is the 'Valid' Bit and is set if the 'Logical block address' in the returned sense data (in R2) is valid. Bits 22..20 are the 'error class' Bits 19..16 are the 'error code' R1 LMB = Bits 15..13 are the 'vendor unique' Bits from byte 1 Bits 12..8 are zero R1 LSB = Bits 7..0 R2 = 'Logical block address' returned in bytes 1..3 of the returned sense data (the vendor unique Bits masked out). R3 = indicates amount of data transfered R4 = amount of data not transfered Extended sense data returned ---------------------------- R1 MSB = the LSB of the RISC OS error number. ie 196..255 R1 = byte 0 of the returned sense data Bit 23 is the 'Valid' Bit and is set if the 'Information bytes' in the returned sense data (now in R2) are valid. Bits 22..20 are the 'error class' Bits 19..16 are the 'error code' R1 = 'segment number' ie byte 1 of the returned sense data R1 byte 2 of the returned sense data Bit7 is 'Filemark' Bit6 is 'EOM' Bit5 is 'ILI' Bit4 is 'reserved' Bits 3..0 hold the 'sense key' R2 = the 'information bytes' returned as bytes 3..6 of the sense data, (byte sex reversed to suit ARM). R3 = indicates amount of data transfered R4 = amount of data not transfered NOTE Bit 23 of R1 always indicates data-in-R2-is-valid, as it is either the 'valid' Bit returned by the request sense command, or zero. ---------------------------------------------------------------------------- The * commands ============== *Devices ======== *Devices displays information on the devices attached to the SCSI bus(es). The resulting display shows the type of each device this can be either "Direct-access", "Sequential-access", "Printer", "Processor", "WORM", "Read-only", "Scanner", "Optical memory", "Changer", Communications", "Unknown", and "Host". The capacity is calculated by multiplying the highest block number by the block size, as returned by a Read Capacity command. The Vendor, Product and Revision fields are provided by the Inquiry command, and are displayed with mimimal formating. An example of the output of this command is shown below; Device Type Capacity Vendor Product Revision 0 Direct-access 18 Mbytes RODIME RO652 5.02 1 2 Direct-access 100 Mbytes CONNER Cp3100-100mb-3.5 0.0C 3 Read-only 27 Mbytes HITACHI CDR 0004 4 5 Direct-access 43 Mbytes RODIME RO3000S 1.24 6 7 Host ACORN SCSI expansion 0000 *ScsiBlock N.B. NOT IMPLEMENTED BY ACORN SCSIdriver ========== *ScsiBlock adr accesskey devID cdb0 cdb1 cdb2... *ScsiBlock issues a SCSI command to the target device. adr is the address data transfer address devID is the SCSI deviceID cbd0 onwards (maximum of 12 parameters) are the bytes of the SCSI command block to be sent. errors unique to this command &0002010F - "Invalid parameters" &00020110 - "Parameter error" Warning ======= The use of SWI SCSI_Control with R0=1 (Abort Op), or the use of command timeouts may prove unreliable with certain versions of the WD33C93A SCSI bus interface controller. The current version of the chip, revision C, is known to exhibit problems, it is expected that later revisions will not. The SBIC has a tendancy to hang if a RaiseATN command (issued by the device driver abort command code) is issued during a data-out phase.