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CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
5 .
2 .
i 5.
READ Command
==============================================================================
Bit:
7
6
5
4
3
2
1
o
Byte :
==============================================================================
o
:
Operation Code (08h)
:
-----1-----------------------------------------------------------------------1
1
I
Logical Unit Number
I
(MSB)
I
-----1------------------------------
---I
2
Logical Block Address
:
---I
3
(LSB)
I
-----------------------------------------------------------------------1
4
Transfer Length
I
-----------------------------------------------------------------------:
5
Control Byte
:
==============================================================================
The READ command requests that the controller transfer data to the
initiator.
The data will be transferred in whole blocks without delays occurring during a
block transfer on the bus.
After completion of the read operation the drive
will enter the hold track state for the duration of the inactivity time.
The logical block address specifies the logical block at which the read
operation will begin.
The transfer length specifies the number of contiguous logical blocks of
data to be transferred.
A transfer length of zero indicates that
256
logical
blocks will be transferred.
Any other value indicates the number of logical
blocks that will be transferred.
This command will be terminated with a RESERVATION CONFLICT status if any
reservation conflict exists and no data will be read.
This command will be terminated with a CHECK CONDITION status for a number
of reasons.
The error recovery parameters determine when and how the data
errors are reported.
See Section 5.3.1.1. The data transfer will also be
terminated with a CHECK CONDITION STATUS if any of the following events occur
while a read operation is in progress.
The sense key will be set to ILLEGAL
REQUEST and the additional sense code set to END OF USER AREA ENCOUNTERED ON
THIS TRACK.
1) A mode zero is detected (i.e. post-gap detected).
2)
An
index equal to 0 is detected (i.e. pre-gap detected).
3)
A track number change is detected (i.e. lead-out, mode one (-) mode two).
4)
A change in bit one of the control field is detected.
If the logical block address requested is not within a data track the
command will be terminated with a CHECK CONDITION status.
The sense key will
be set to ILLEGAL REQUEST and the additional sense code set to ILLEGAL MODE
FOR THIS TRACK.
5-29
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