Chapter 5
S Mode Functions
© National Instruments Corp.
5-23
GPIB-SCSI-A User Manual
cmd - Send GPIB Commands
Type:
Specialized Controller function
Purpose:
Use
cmd
when the I/O and bus management functions do not
meet the needs of your device.
cmd
gives you precise control
over the GPIB. For example, in applications that require
command sequences not sent by other I/O or bus management
functions,
cmd
allows you to transmit any sequence of
interface messages (commands) over the GPIB.
Format:
Bit
7
6
5
4
3
2
1
0
Byte
0
Opcode = C4H
1
Reserved
2
Reserved
3
Most Significant Byte of Command Count
4
Least Significant Byte of Command Count
5
Reserved
Remarks:
Command Count is a 16-bit unsigned number representing the
number of GPIB command bytes (interface messages) to send.
These commands are represented by their ASCII character
equivalents. For example, the GPIB Untalk (UNT) command
is the ASCII character underscore (_).
The GPIB commands, or interface messages, are listed in
Appendix A. They include device talk and listen addresses,
secondary addresses, messages, device clear and trigger
instructions, and other management messages.
Do not use
cmd
to send programming instructions to devices.
Use
rd
,
wrt
,
brd
, and
bwrt
to send or receive
programming instructions and other device-dependent
information.
