National Instruments GPIB-PC - Manual (Page 109)

BASICA/QuickBASIC GPIB-PC Function Calls Section Four A
GPIB-PC User Manual 4A-34 ©National Instruments Corp.
BASICA/QuickBASIC BASICA/QuickBASIC
IBGTS IBGTS
Purpose: Go from Active Controller to Standby
Format: CALL IBGTS (BD%,V%)
Remarks: BD% specifies an interface board. If V% is non- zero, the
GPIB-PC shadow handshakes the data transfer as an
Acceptor, and when the END message is detected, the
GPIB-PC enters a Not Ready For Data (NRFD) handshake
holdoff state on the GPIB. If
V% is zero, no shadow
handshake or holdoff is done.
The IBGTS function causes the GPIB-PC to go to the
Controller Standby state and to unassert the ATN signal if
it initially is the Active Controller.
IBGTS permits GPIB
devices to transfer data without the GPIB-PC being a party
to the transfer.
If the shadow handshake option is activated, the GPIB-PC
participates in data handshake as an Acceptor without
actually reading the data. It monitors the transfers for the
END (EOI or end-of-string character) message and holds off
subsequent transfers. This mechanism allows the GPIB-PC
to take control synchronously on a subsequent operation
such as
IBCMD or IBRPP .
Before performing an IBGTS with shadow-handshake, the
IBEOS function should be called to establish the proper
end-of-string character or to disable EOS detection if the
end-of-string character in use by the talker is not known.
The ECIC error results if the GPIB-PC is not CIC.
Refer also to IBCAC .
In the example that follows, GPIB commands and
addresses are coded as printable ASCII characters. When
the hex values to be sent over the GPIB correspond to
printable ASCII characters, this is the simplest means of
specifying the values. Refer to Appendix A for conversions
of hex values to ASCII characters.