Measurement Computing GPIB-488 - Manual (Page 23)

Chapter 3 GPIB 488.1 Library Reference
Programming Reference Manual 3-10 GPIB-488
IBCMDA
Transfers GPIB commands asynchronously from a string.
Syntax
C ibcmda (int board, char cmnd[], long bytecount)
Parameters
board is an integer containing the board handle.
cmnd is thecommand string to be sent. This string is comprised of GPIB multiline
commands.These commands are listed in Appendix A, Multiline Interface Messages .
bytecount is the number of command bytes to be transferred. Note that in C, although this
parameter is of type long, integer values and variables can also be passed.
Returns
ibsta will contain a 16-bit status word as described in Appendix B, IBSTA .
iberr will contain an error code, if an error occurred. An ECIC error is generated if the GPIB
Interface Board specified is not the Active Controller. If no listening devices are found, the
ENOL error is returned.
ibcnt , ibcntl will contain the number of bytes that were transferred. ibcnt is a 16-bit
integer. ibcntl is a 32-bit integer. If the requested count was greater than 64 K, use ibcntl
instead of ibcnt .
Usage Notes
This routine passes only commands. It is not used to transmit programming instructions (data)
to devices. Use the
ibrd / ibwrt routines for this purpose.
Asynchronous I/O is not explicitly supported and will be treated as synchronous.
Example
This example prepares the board to talk and addresses three devices (at addresses 8, 9, and
10) to listen.
ibcmda executes in the background and the program continues into the WHILE
loop. This loop calls ibwait to update ibsta and checks ibsta to see if ibcmda has
completed or an error has occurred. The program may do anything within the WHILE loop
except make other GPIB I/O calls.
C char command[] = "\0x3f\0x5f\0x40\0x28\0x29\0x2a"
ibcmda (board, command, 6);
while ( (ibsta & CMPL+ERR) == 0)
ibwait (board, 0);