National Instruments GPIB-SCSI-A, Руководство пользователя

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S Mode Functions Chapter 5
GPIB-SCSI-A User Manual 5-110 © National Instruments Corp.
wrt - Write Data *
Type: High-level I/O Function
Purpose: Use
wrt
to send data over the GPIB. All GPIB addressing is
performed automatically.
Format:
Bit 7 6 5 4 3 2 1 0
Byte
0 Opcode = DBH
1 GPIB Primary Address High 3 bits of Cnt
2 GPIB Secondary Addr. (Opt.) Mode 2 bits of Cnt
3 Middle Byte of Count
4 Least Significant Byte of Count
5 Reserved
Remarks: The argument GPIB Primary Address along with the GPIB
Secondary Address indicates the address of the device to
which the GPIB-SCSI-A attempts to write data. To indicate
that GPIB Secondary Address contains a valid device address,
set Mode to 1. Count is a 21-bit unsigned count that
represents the number of bytes to write. Therefore, Count can
represent a number between 0 and 2,097,152.
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.