National Instruments GPIB-PC User Manual
Page 68
Section Four
GPIB-PC Functions — Overview
©National Instruments Corp.
4-7
GPIB-PC User Manual
It is also returned when an invalid unit descriptor is passed
to any function call. In this case, the variable
IBCNT
will
contain the DOS error code 6, "
Invalid handle
." The
remedy is to be sure that
IBFIND
has been called and that
it returned successfully. Also note that following a call to
IBONL
with a second argument of 0, which places
bd
"offline," an
IBFIND
is required before any subsequent
calls with that device or board.
EDVR is also returned when the handler (
GPIB.COM
) is
not installed. The remedy is to check the
CONFIG.SYS
file in the root directory and make sure it contains the line:
DEVICE=GPIB.COM
ECIC (1)
ECIC is returned when one of the following board level
calls is made while the board is not CIC of the GPIB:
•
IBCMD
,
•
IBRPP
,
•
IBCAC
, and
•
IBGTS
.
In cases when the GPIB-PC should always be the CIC, the
remedy is to be sure to call
IBSIC
to send Interface Clear
before attempting any of these calls, and to avoid sending
the command byte TCT (hex 09, Take Control). In
multiple CIC situations, the remedy is to always be certain
that the CIC bit appears in the status word
IBSTA
before
attempting these calls. If it is not, it is possible to perform
an
IBWAIT
(CIC) call to delay further processing until
control is passed to the board.
ENOL (2)
ENOL usually occurs when a write operation was attempted
with no listeners addressed. For a device write, this error
indicates that the GPIB address configured for that device
in the handler does not match the GPIB address of any
device connected to the bus. This situation may be
corrected by either attaching the appropriate device to the
GPIB, by modifying the address of an already attached
device, by altering the switches on the device, by calling
IBPAD
(and
IBSAD
if necessary) to make the configured
address match the device switch settings, or by using the
IBCONF
configuration utility to reassign the proper GPIB