User Manual

G-4 GPIB 488.1 Protocol 2400 Series SourceMeter

User’s Manual

Using SCPI-based programs

In general, an existing SCPI-based program will run properly and faster in the

488.1 protocol as long as it meets the above guidelines and limitations.

NRFD hold-off

*OPC, *OPC?, and *WAI are still functional but are not needed for the 488.1 pro-

tocol. When sending commands, the GPIB is automatically held off when it

detects a terminator. The hold-off is released when all the commands have fin-

ished executing, or if there is some parser or command error. An exception is an

initiate command, which releases the hold-off immediately and does not wait for

all of the readings to be acquired. This immediate release of bus hold-off is done

to support GET, SDC, IFC, *TRG, *RCL, *RST, SYSTem:PRESet, and ABORt

during data acquisition.

NDAC hold-off

NDAC hold-off is included with the GPIB 488.1 protocol mode to allow a single

instrument to hold off all others on the bus until it is finished executing a com-

mand. The following command controls NDAC hold-off:

SYSTem:MEP:HOLDoff ON | OFF

The default is OFF, but NRFD hold-off will still be enabled and will prevent an

instrument from accepting further commands. See Figure G-1 for the complete

IEEE-488 handshake sequence.

Figure G-1

IEEE-488 handshake sequence

DATA

DAV

SOURCE

VALID

ALL READY

ACCEPTOR

NRFD

NDAC

ALL ACCEPTED

ACCEPTOR