Section Four A
BASICA/QuickBASIC GPIB-PC Function Calls
©National Instruments Corp.
4A-17
GPIB-PC User Manual
BASICA/QuickBASIC
BASICA/QuickBASIC
IBCAC
IBCAC
Purpose:
Become Active Controller
Format:
CALL IBCAC (BD%,V%)
Remarks:
BD%
specifies an interface board. If
V%
is non-zero, the
GPIB-PC takes control synchronously with respect to data
transfer operations; otherwise, the GPIB-PC takes control
immediately (and possibly asynchronously).
To take control synchronously, the GPIB-PC asserts the
ATN signal in such a way as to ensure that data being
transferred on the GPIB is not corrupted. If a data
handshake is in progress, the take control action is
postponed until the handshake is complete; if a handshake
is not in progress, the take control action is done
immediately. Synchronous take control is not guaranteed if
an
IBRD
or
IBWRT
operation completed with a timeout or
error.
Asynchronous take control should be used in situations
where it appears to be impossible to gain control
synchronously (e.g., after a timeout error).
It is generally not necessary to use the
IBCAC
function in
most applications. Functions such as
IBCMD
and
IBRPP
,
which require that the GPIB-PC take control, do so
automatically.
The ECIC error results if the GPIB-PC is not CIC.
Board Examples:
1.
Take control immediately without regard to any data handshake
in progress.
100 V% = 0
110 CALL IBCAC (BRD0%,V%)
120 REM IBSTA% should show that the
130 REM interface board is now CAC, i.e.,
140 REM CIC with ATN asserted.