National Instruments GPIB-SCSI-A, Руководство пользователя

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Chapter 5 S Mode Functions
© National Instruments Corp. 5-65 GPIB-SCSI-A User Manual
rd (continued)
analyze the GPIB-SCSI-A status that contains a count equal to
the exact number of bytes read from the GPIB. This number
represents the number of valid data bytes received.
The
rd
operation terminates when:
• The GPIB-SCSI-A successfully reads all data.
• The GPIB-SCSI-A detects an error.
• The I/O time limit is exceeded.
• The END message is detected.
• The EOS character is detected (if this option is enabled).
• The Device Clear (DCL) or Selected Device Clear (SDC)
command is received from another device that is
Controller-In-Charge (CIC).
After
rd
terminates, the GPIB-SCSI-A records the number of
data bytes it actually read from the GPIB. If one of the events
above occurs (except if the GPIB-SCSI-A successfully reads
all data), the count may be less than expected.
If the GPIB-SCSI-A is CIC,
rd
causes the GPIB-SCSI-A to
address itself to listen if it is not already addressed. The
GPIB-SCSI-A also addresses the device indicated by the
address values in the CDB to talk.
The GPIB-SCSI-A then places itself in Standby Controller
state with ATN* off and remains there after the read operation
is complete.
The GPIB-SCSI-A must be CIC to perform the addressing. If
this is the first function you call that requires GPIB Controller
capability, and you have not disabled System Controller
capability with
rsc
, the GPIB-SCSI-A sends Interface Clear
(IFC*) to make itself CIC. It also asserts Remote Enable.