National Instruments GPIB-SCSI-A, Руководство пользователя

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S Mode Functions Chapter 5
GPIB-SCSI-A User Manual 5-10 © National Instruments Corp.
bwrt - Board Level Write Data
Type: Low-level I/O Function
Purpose: Use
bwrt
to send data over the GPIB. This command
assumes that the GPIB-SCSI-A has been previously addressed
to talk.
Format:
Bit 7 6 5 4 3 2 1 0
Byte
0 Opcode = DCH
1 Most Significant Byte of Transfer Count
2 Middle Most Significant Byte of Transfer Count
3 Middle Least Significant Byte of Transfer Count
4 Least Significant Byte of Transfer Count
5 Reserved
Remarks: Count is a 4-byte unsigned count that represents the number of
bytes to write to the GPIB. Therefore, Count can represent a
number between 0 and 4,294,967,295.
All data received from the SCSI Initiator during the Data Out
phase is passed to the GPIB Listeners. If an error occurs with
the GPIB, the GPIB-SCSI-A stops attempting to transfer data
from the SCSI to the GPIB. Instead, the GPIB-SCSI-A
finalizes processing of the command according to Switch 5 of
configuration switch SW2. If Switch 5 is OFF, the
GPIB-SCSI-A reads all the data from the SCSI Initiator until
the count requested is exhausted. If Switch 5 is ON, the
GPIB-SCSI-A immediately changes to the Status phase
without transferring additional data.
The
bwrt
operation terminates when one of the following
events occurs:
• The GPIB-SCSI-A successfully transfers all data