User`s guide

Page 56

Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)

5.4.3. Table [3]: Discrete Control Mode (Open/Close/Stop)

Words [4  63] PLC access: Read / Write

This table commands the actuator to move the valve either OPEN / CLOSED / STOP.

There are three discrete valve control commands available:

1. 1 (0x0001) for Open

2. 2 (0x0002) for Close

3. 3 (0x0003) for Stop now at the current location.

The 1746-C will only react to these values.

The mechanism used to execute these commands is:

• If (OPEN) command: a setpoint of 4095 is transmitted to the actuator.

• If (CLOSE) command: a setpoint of 0 is transmitted to the actuator.

• If (STOP) command:

o A Modbus command is sent to the actuator to read the current position.

o That “current” position is sent to the actuator as the setpoint to go to.

A read back of Table [3] will

• If a write command issued: reflect the write command accepted by the 1746-C

• If a read command issued: reflect the last status of the discrete commands (unless changed by

a new table [5] entry).

Note 1: While the table will accept any value, any illegal data will be ignored.

Note 2: Any NEW discrete control command in this table will change the corresponding setpoint

control value in Table [5] to either 0 / 4095 / or “current position”.

Note 3: If a NEW change setpoint command is issued in Table [5] for a particular valve, then the

corresponding discrete control command in this table (Table [3]) will be zeroed out.