Appendix A
Status Word Conditions
© National Instruments Corp.
A-3
NI-488.2M UM for Windows NT
RQS (dev)
RQS appears in the status word only after a device-level call and indicates that the device
is requesting service. RQS is set whenever bit 6 is asserted in the serial poll status byte
of the device. The serial poll that obtains the status byte can be the result of a call to
ibrsp
, or the poll might be automatic if automatic serial polling is enabled. Do not
issue an
ibwait
on RQS for a device that does not respond to serial polls. RQS is
cleared when an
ibrsp
reads the serial poll status byte that caused the RQS.
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 serial 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.