Manual

Remote Interface Reference

RS-232/422 Configuration

5.2.6.1 Using the *OPC Command

The *OPC command is executed within the normal command queue. Upon

completed execution of the *OPC command, the “Operation Complete” bit

(bit 0) of the Standard Event register will be set.

If the operator has so configured the Standard Event and Status Byte

enable registers, the *OPC command can generate a service request when

execution completes (see Figure 5-1). 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:

PERCENT; CH1:ALARM:HI 90.0; CH1:ALARM:LO 10.0; *OPC;

The above example sets the remote units to percent, the Channel 1 “HI”

alarm to 90.0%, the Channel 1 “LO” alarm to 10.0%, and sends *OPC as the

4th command for determining when execution all of the commands

(including *OPC) has completed.

5.2.6.2 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 requesting remote

interface when executed. Using *OPC? is often the most straightforward

solution for determining completed command execution. It is also

unambiguous since the result is returned directly to the requesting remote

communication interface.

5.2.7 Remote Units

The Model 286 supports a remote units setting that is maintained

separately from the units selected via the front panel keypad. The remote

units setting is retained between power-ups. If the PERCENT command is

sent to the remote interface, the remote units for both remote interfaces is

set to percent. All alarm values should then be sent as a percent value, and

all return level data and alarm queries are returned in units of percent.

The UNITs? query returns the currently selected remote units (e.g. the

percent setting would return 0,”PERCENT”).

5.3 RS-232/422 Configuration

The Model 286 allows the baud rate of the RS-232/422 interface to be

configured by the user. See the menu description in paragraph 4.3.12.3 on