Measurement-computing GPIB-488 Manuel d'utilisateur télécharger pdf (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);

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Measurement-computing GPIB-488 Manuel d'utilisateur Page 23