National Instruments GPIB-PC User Manual
Page 64
Section Four
GPIB-PC Functions — Overview
©National Instruments Corp.
4-3
GPIB-PC User Manual
ERR (db)
ERR is set in the status word following any call that results
in an error; the particular error may be determined by
examining the IBERR variable. It is cleared following any
call that does not result in an error.
NOTE: Always check for an error condition after each call.
An error made early in your application program may not
become apparent until a later instruction. At that time, the
error can be more difficult to locate.
TIMO (db) TIMO specifies whether a timeout has occurred. It is set in
the status word following a call to
IBWAIT
if the TIMO bit
of the
IBWAIT
mask
parameter is also set and if the wait
has exceeded the time limit value that is set by the
IBTMO
call. It is also set following a call to any of the synchronous
I/O functions (e.g.,
IBRD
,
IBWRT
, and
IBCMD
) if a timeout
occurs during a call. TIMO is cleared in the status word in
all other circumstances.
END (db)
END specifies whether the END or EOS message has been
received. It is set in the status word following a read
function if the END or EOS message was detected during
the read. While the GPIB-PC is performing a shadow
handshake as a result of the
IBGTS
function, any other
function call may return a status word with the END bit set
if the END or EOS message occurred before or during that
call. It is cleared in the status word when any I/O operation
is initiated.
SRQI (b)
SRQI specifies whether a device is requesting service. It is
set in the status word whenever the GPIB-PC is CIC and
the GPIB SRQ line is asserted. It is cleared whenever the
GPIB-PC ceases to be the CIC, or the GPIB SRQ line is
unasserted. The bit is also cleared when executing board
functions and the GPIB-PC is an active talker, i.e., it is
addressed to talk and ATN is unasserted.
In Revision D software, the SRQI status bit always reflects
the current level of the SRQ line whether or not the GPIB-
PC is CIC.