User`s guide

Page 120

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

Example (in byte order) of a request to

force coil 173 (internal coil number 172)

“ON” in slave device 17:

1. Slave Address 11

2. Function 05

3. Coil Address Hi byte 00

4. Coil Address Lo byte AC

5. Force Data Hi byte FF

6. Force Data Lo byte 00

7. CRC Hi byte ––

8. CRC Lo byte ––

NOTE: 172 decimal = 0xAC

6.5.2.3. Modbus Function Code 05 … Set (Force) Single Coil

Using function code 05, the Modbus master (host) may directly address and write single bits that indicate

coils … to turn them ON or OFF.

Writing to a Read Only (RO) coil will

• Have no affect on valve operation

• Be ignored by the application software.

• Cause the actuator to return a response indicating “illegal function code”.

If a configuration coil is set which is dependent upon other configuration coils being set (and the other

coils are not set), a configuration error will be indicated that prevents valve actuator control.

When a valid configuration is written, the controller compares the state of the coil to the state stored in

EEPROM. If the state has changed, the new state is stored to EEPROM configuration.

Refer to the previous section that identifies “

Standard Coils”

Response example (in byte order):

1. Slave Address 11

2. Function 05

3. Coil Address Hi 00

4. Coil Address Lo AC

5. Force Data Hi FF

6. Force Data Lo 00

7. CRC Hi byte ––

8. CRC Lo byte ––