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Appendix A Status Word Conditions
© National Instruments Corp. A-3 NI-488.2 User Manual for Windows
An automatic serial poll occurs either as a result of a call to ibwait, or automatically, if
automatic serial polling is enabled. If the serial poll response queue is not empty, ibrsp
returns the oldest byte stored in the queue. To empty the response queue, call ibrsp
repeatedly until RQS is no longer set in the device's status word.
SPOLL (brd)
Use SPOLL in Talker/Listener applications to determine when the Controller has serial
polled the GPIB board. The SPOLL bit is disabled by default. Use the ibconfig
function (option IbcSPollBit) to enable it. When this bit is enabled, it is set after the
board has been polled. SPOLL is cleared on any call immediately after an ibwait call,
if the SPOLL bit was set in the wait mask, or immediately following a call to ibrsv.
EVENT (brd)
Use EVENT in Talker/Listener applications (applications in which the GPIB interface is
not the Controller) to monitor the order of GPIB device clear, group execute trigger, and
send interface clear commands. The usual DCAS and DTAS bits of ibsta might be
insufficient.
The EVENT bit is disabled by default. If you want to use this bit, you must use the
ibconfig function (option IbcEventQueue) to enable it. When you enable this bit,
the DCAS and DTAS bits are disabled. When an event occurs, this bit is set and any I/O
in progress is aborted. The application can then call the ibevent function to determine
which event occurred.
CMPL (dev, brd)
CMPL indicates the condition of I/O operations. It is set whenever an I/O operation is
complete. CMPL is cleared while the I/O operation is in progress.
LOK (brd)
LOK indicates whether the board is in a lockout state. While LOK is set, the
EnableLocal routine or ibloc function is inoperative for that board. LOK is set
whenever the GPIB board detects that the Local Lockout (LLO) message has been sent
either by the GPIB board or by another Controller. LOK is cleared when the System
Controller unasserts the Remote Enable (REN) GPIB line.