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COMMON COMMAND SET AND DISK OPERATION
A-16
A
Before accessing a floppy disk on the OMTI7000, the MVME147 SCSI firmware
sends a mode select command to the controller. Below is the command
descriptor block for the mode select command:
Mode Select Command CDB
The first twelve bytes that are transferred during the DATA OUT phase for the
mode select command make up the mode select header, and the block
descriptor which is described below:
Mode Select Header and Block Descriptor
NOTES:
1. Number of cylinders is taken from the attach packet byte
offset $08.
2. Number of heads is taken from the attach packet byte offset
$07.
3. Starting cylinder - write precomp is taken from the attach
packet byte offset $0A.
4. Starting cylinder - reduced write current is left as the
default value as returned from the mode sense command.
5. The drive step rate is specified in the attach packet, byte
offset $05 in units of 40 microseconds. This value is
converted to 100 nanoseconds units before writing to page
4 of the mode select command. A value of zero in the
attach packet causes the drive to use the default value.
6. Landing zone cylinder is left as the default value as
returned from the mode sense command.
7. This field is left as the default value as returned from the
mode sense command.
BYTE OFFSET
VALUE COMMENTS
0 15 Command code
1 10 LUN = 0, PF = 1, SP = 0
200Reserved
300Reserved
4 2C Parameter list length
5 00 Control byte: no link, no flag