Measurement Computing GPIB-488 - Manual (Page 12)

Chapter 2 Programming with the GPIB Library
GPIB-488 2-3 Programming Reference Manual
Board l/O
In comparison, the Board I/O routines are low-level routines. If you use
them, you must understand how the GPIB operates in detail. Generally, the
only time you need to use Board I/O is if it is impossible to perform the
same operation using device I/O, such as passing control from one
controller to another.
To perform the same task as the seven steps outlined in Device vs. Board
I/O (send a command to a device), you need to know the codes for the
various forms of addressing and the codes for the GPIB Unlisten and
Untalk commands.
Use the routines in this sequence:
ibfind —to open the board
ibcmd —to send the address of the talker and listener
ibwrt —to send the command to the device
ibcmd —to send the address of the talker and listener
ibrd —to read the data back from the device
ibcmd —to send the Unlisten (UNL) and Untalk (UNT) commands
Device Handles
Most of the routines in the 488.1 library have a device handle as the first
argument. The first GPIB call in your program is usually
ibfind . This
routine "opens" a board or device and returns a GPIB board or device
handle. If you pass the name of a board, it returns a board handle. Likewise,
if a device name is passed, a device handle is returned. Some library
routines only work with device handles, some only with board handles, and
some with both.