AMI 420, Installation, Operation And Maintenance Instructions, Page: 93 / 134

Rev. 7
75
Remote Interface Reference
Command Handshaking
If the operator has so configured the Standard Event and Status Byte
enable registers, the
*OPC
command can generate an IEEE-488 service
request when execution completes (see Figure 4-1). If using the serial port,
the
*OPC?
query is a better alternative since a response is returned
directly to the requesting communications interface.
An example of a sequence of commands using the
*OPC
command to
handshake is the following:
CONF:RAMP:CURR 50.0, 0.1; CONF:VOLT:LIM 5.0; *OPC;
The above example sets the programmed current to 50.0 A, the ramp rate
to 0.1 A/s, the voltage limit to 5.0 V, and sends as the third command the
*OPC
command for determining when execution all of the commands
(including
*OPC
) is completed. If the Standard Event and Status Byte
enable registers are correctly configured, the
*OPC
command will then
result in an IEEE-488 service request when execution completes.
Alternately, the Serial Poll function of the IEEE-488 bus may be used to
determine completion of the command.
4.2.4.2 Using the
*OPC?
Query
The
*OPC?
query is similar to the
*OPC
command, but instead of setting
the “Operation Complete” bit of the Standard Event register, the
*OPC?
query returns a “1” (plus termination characters) to the appropriate output
buffer when executed. Using
*OPC?
is often the simpler solution for
determining completed command execution. It is also unambiguous during
simultaneous serial and IEEE-488 operation since the result is returned
directly to the requesting communication interface.