GPIB-PC Functions — Overview
Section Four
GPIB-PC User Manual
4-8
©National Instruments Corp.
address to the device in the handler.
For a board write, an
IBCMD
call is generally necessary to
address devices before an
IBWRT
. Be sure that the proper
listen address is in the
IBCMD
argument string and that no
Unlisten (hex 3F) command follows it.
ENOL may occur in situations in which the GPIB-PC is not
the CIC and the Controller asserts ATN before the write
call in progress has ended. The remedy is either to reduce
the write byte count to that which is expected by the
Controller, or to resolve the situation on the Controller's
end.
EADR (3)
EADR occurs when the GPIB-PC is CIC and is not
addressing itself before read and write calls are made. This
error is extremely unlikely to occur on a device call. For a
board call the remedy is to be sure to send the appropriate
Talk or Listen address using
IBCMD
before attempting the
IBWRT
or
IBRD
.
EADR is also returned by the function
IBGTS
when the
shadow-handshake feature is requested and the GPIB ATN
line is already unasserted. In this case, the shadow
handshake is not possible and the error is returned to notify
you of that fact.
IBGTS
should almost never be called
except immediately after an
IBCMD
call. (
IBCMD
causes
ATN to be asserted.)
EARG (4)
EARG results when an invalid argument is passed to a
function call. The following are some examples:
IBTMO
called with a value not in the range 0-17.
IBEOS
called with meaningless bits set in the high byte of
the second parameter.
IBPAD
or
IBSAD
called with illegal addresses.
IBPPC
called with illegal parallel poll configurations.
A board-only call made with a valid device descriptor, or a
device-only call made with a valid board descriptor.
(NOTE: EDVR is returned if the descriptor is invalid.)
ESAC (5)
ESAC results when
IBSIC
or
IBSRE
is called when the