Read Cdp (E4H) - Pioneer SCSI-2 Reference Manual

Read CDP

2.24 Read CDP (E4h)

Operation Code is (E4h)
This command requests the drive to return the status data resulting from the previous WRITE
CDP command. The drive terminates the data phase when Allocation Length bytes or all the
relevant data have been transferred.
The last status data returned from the Drive Controller is buffered in the drive SCSI controller.
Because the next return data from the next WRITE CDP command will overwrite the buffer, the
READ CDP command should immediately follow a WRITE CDP command.
The buffered status data is cleared after executing a READ CDP command. If a READ CDP
command is issued after the buffer is cleared, the drive does not go to the data phase, but returns
a GOOD status.
If a READ CDP command is issued during the execution of a player operation, a BUSY status is
returned. Any command other than the READ CDP is accepted. If the drive receives a SCSI
command (except the INQUIRY or REQUEST SENSE commands) the action initiated by the
WRITE CDP command will be terminated. In this case, the player status returned by the READ
CDP command will be "E16" (Input From Other Device). Such a player interrupt does not cause
any SCSI errors.
See Appendix B for information on the CDP return codes.
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