National Instruments GPIB-SCSI-A User Manual page 70

Chapter 5
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Build SCSI Command Descriptor Block (CDB)
Byte 0 = [hex value]
Byte 1 = [hex value]
Byte 2 = [hex value]
Byte 3 = [hex value]
Byte 4 = [hex value]
Byte 5 = [hex value]
In this step, you should use a data structure that provides six
consecutive 8-bit bytes. For example, an array of bytes.
•
SCSIArbitrate
Attempt to gain control of the SCSI. If the SCSI is not in the Bus Free
phase or there is another Initiator with a higher priority arbitrating, you
will not gain control of the SCSI.
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SCSISelect(GPIB-SCSI-A id)
Select the GPIB-SCSI-A with the SCSI ATN* signal not asserted.
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SCSISelectATN(GPIB-SCSI-A id)
Select the GPIB-SCSI-A with the SCSI ATN* signal asserted.
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SCSIMesgOut([IDENTIFY message])
If the GPIB-SCSI-A is selected with the ATN* line asserted, the first
phase it enters is the Message Out phase. The message sent here
should be the IDENTIFY message. If you want to indicate support of
disconnection/reconnection, bit 6 in the IDENTIFY message should be
set (for example, 0xC0).
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SCSICmd(CDB)
Send the Command Descriptor Block to the GPIB-SCSI-A. The
GPIB-SCSI-A interprets the command requested and starts processing
the command.
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SCSIStatus(Sbyte)
To indicate the completion of the command, the GPIB-SCSI-A goes
into the Status phase to deliver a status byte pertaining to the last
command request.
© National Instruments Corp. 5-3 GPIB-SCSI-A User Manual
S Mode Functions