Despatch Protocol Plus Modbus Communications User Manual

Page 25

Chromalox Instruments and Controls

A-51643 Rev. 6 10/06/03

1. Send an individual function code 08, sub-function 10 queries (clear communication counters) to each

slave on the network.

2. Perform desired broadcast functions.

3. Send an individual function code 08, sub-function 14 queries (return slave message count) to each

slave on the network.

4. If the number of processed messages in each slave matches the number of broadcasts sent then the

broadcast messages were sent reliably.

4.12 Communication Parameter Adjustments

If the communication parameters (slave address, mode, baud rate, or parity) are changed through the front

panel or through the Modbus link, the controller need not be reset. The new parameters (in the controller)

will become effective on the next query/response cycle. However, in some cases, the first query after

changing the settings may not generate a response as this query is used to reset the communication setup.

The user is responsible for setting the master device to the proper settings.

Setting the communications mode to ―disabled‖ will immediately disable communications.

Communications can only be re-enabled through the front panel keypad. Use the force listen mode