National Instruments GPIB-PC - Manual (Page 75)

GPIB-PC Functions — Overview Section Four
GPIB-PC User Manual 4-14 ©National Instruments Corp.
If the handler is configured with automatic serial polling enabled, this
feature will be disabled after a board-level I/O function call, and
resumed after a device-level I/O function call. However, if any device-
level I/O call results in a timeout error, this feature will be disabled
until the next I/O call completes.
NOTE: If the RQS bit of the device status word is still set after IBRSP
is called, the response byte queue has at least one more response byte
remaining.
IBRSP should be called until RQS is cleared to gather all
stored response bytes and to guard against queue overflow.