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Section Four GPIB-PC Functions — Overview
©National Instruments Corp. 4-5 GPIB-PC User Manual
as a Talker. It is sent either by the GPIB-PC itself or by
another Controller. It is cleared whenever the GPIB-PC
detects the Untalk (UNT) command, a talk address other
than its own talk address, or Interface Clear (IFC).
LACS (b) LACS specifies whether the GPIB-PC has been addressed
as a Listener. It is set whenever the GPIB-PC detects its
listen address (and secondary address, if enabled) has been
sent either by the GPIB-PC itself or by another Controller.
It is also set whenever the GPIB-PC shadow handshakes as
a result of the IBGTS function. It is cleared whenever the
GPIB-PC detects the Unlisten (UNL) command, its own
talk address, Interface Clear (IFC), or IBGTS is called
without shadow handshake.
DTAS (b) DTAS specifies whether the GPIB-PC has detected a
device trigger command. It is set whenever the GPIB-PC,
as a Listener, detects the Group Execute Trigger (GET)
command has been sent by another Controller. It is cleared
in the status word on any call immediately following an
IBWAIT call if the DTAS bit is set in the IBWAIT mask
parameter.
DCAS (b) DCAS specifies whether the GPIB-PC has detected a
device clear command. It is set whenever the GPIB-PC
detects the Device Clear (DCL) command has been sent
by another Controller, or whenever the GPIB-PC as a
Listener detects the Selected Device Clear (SDC)
command has been sent by another Controller. It is cleared
in the status word on any call immediately following an
IBWAIT call if the DCAS bit was set in the IBWAIT mask
parameter, or on any call immediately following a read or
write.
In addition to the above, the following situations also affect the status
word bits:
• A call to the function IBONL clears the following bits:
END LOK REM CIC TACS LACS DTAS DCAS
• A call to IBONL affects bits other than those listed here
according to the rules explained above.
In the event that a function call returns an ENEB or EDVR error, all
status word bits except the ERR bit are cleared, since these error codes
indicate that it is not possible to obtain the status of the GPIB-PC.