National Instruments GPIB-232, User Manual

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Chapter 5 S Mode Functions — cac
GPIB-232/485CT-A User Manual 5-2 www.ni.com
cac
Become Active Controller
Type
Low-level bus management function
Syntax
cac [bool]
<CR>
Purpose
You can use
cac
to change the GPIB-232/485CT-A from Standby Controller to Active
Controller when the I/O and high-level bus management functions do not meet the needs of
your device.
cac
gives you more precise control over the GPIB than the I/O and high-level
bus management functions.
Remarks
If the argument
bool
is 0, the GPIB-232/485CT-A takes control immediately—that is, it takes
control asynchronously. If the argument
bool
is 1, the GPIB-232/485CT-A takes control after
any handshake that is in progress completes–that is, it takes control synchronously.
If you call
cac
without an argument, the GPIB-232/485CT-A returns the current Controller
status. The Controller status is 0 if the GPIB-232/485CT-A is not the Active Controller and
1 if the GPIB-232/485CT-A is the Active Controller.
The GPIB-232/485CT-A must be CIC when you call
cac
with an argument. If you call
cac
with an argument and the GPIB-232/485CT-A is not CIC, the GPIB-232/485CT-A records the
ECIC error.
The power-on Controller status of the GPIB-232/485CT-A is Idle Controller.
See Also
gts
and
sic
.
Example 1
PRINT #1,"cac 0" 'Take control immediately.
Example 2
PRINT #1,"cac 1" 'Take control synchronously.