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COMMON COMMAND SET
AND DISK OPERATION
The first high level command required to interface with a Winchester disk is
an ATTACH. An ATTACH initializes the SCSI firmware pointers and internal
flags. A RAM work area is used to build the SCSI command descriptor block,
messages sent in the message-out phase, and a place to put incoming
messages, and status. This area also contains a copy of the ATTACH packet
parameters, and two work areas to for mode sense current values and
changeable values.
The ATTACH command performs the following to a Winchester disk:
If bit 5 of attribute word is "1" (byte offset $10), The firmware sends a Reserve
Device SCSI Command ($16) to the SCSI device.
Reserve Command CDB
NOTE: Third party reservation not supported.
If the controller code (byte offset $12) is $17 (synchronous CCS), and if this is
the first ATTACH for this device, the firmware sends an identify message
followed by a synchronous data transfer request message and a test unit ready
command.
Synchronous Data Transfer Request Message
BYTE OFFSET
VALUE COMMENTS
0 16 Command code
1 00 (Note) LUN is inserted into bits 7-5
200 Reserved
300 Reserved
400 Reserved
5 00 Control byte: no link, no flag
BYTE
VALUE COMMENTS
0 C0 Identify with reselection
message