Measurement-computing GPIB-488 Bedienungsanleitung PDF herunterladen (Seite 49)

Chapter 3 GPIB 488.1 Library Reference

Programming Reference Manual 3-36 GPIB-488

IBRDA

Reads data asynchronously from a device/interface board into a string.

Syntax

C ibrda (int boarddev, char buf[], unsigned long

bytecount)

Parameters

boarddev is an integer containing the device/board handle.

buf is the storage buffer for the data. Up to 4 gigabytes-1 (2

-1 bytes) can be stored. String

size may be limited by the language you are using. Check documentation for your language.

bytecount specifies the maximum number of bytes to read.

Returns

ibsta will contain a 16-bit status word as described in Appendix B, IBSTA.

iberr will contain an error code of the first error detected, if an error occurred. An EADR

results if the specified GPIB board is an Active Controller but has not been addressed to listen.

EABO error results if a timeout occurs.

ibcnt, ibcntl will contain the number of bytes that were read. ibcnt is a 16-bit integer.

ibcntl is a 32-bit integer. If the requested count was greater than 64 K, use ibcntl instead

ibcnt.

Usage Notes

Asynchronous I/O is not explicitly supported and will be treated as synchronous.

Example

In this example, ibwrt sends the command "DUMP" to a device. The device responds by

sending back a large block of data.

ibrda begins a transfer of 5000 bytes in the background

and the program continues on into the WHILE loop. The WHILE loop calls

ibwait with

MASK set to 0 to update IBSTA. The WHILE loop checks IBSTA to see if ibrda has

completed, or if an error has occurred. The program may do anything else within the WHILE

loop except make other GPIB I/O calls.

C char *readbuffer[5000];

ibwrt (device, "DUMP");

ibrda (device, readbuffer, 5000);

while ( (ibsta & CMPL+ERR) == 0)

ibwait (device, 0)

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Measurement-computing GPIB-488 Bedienungsanleitung Seite 49