HRX-OM-W004
Chapter 3 Serial communication
HRR Series 3.4
MODBUS communication function
3-3
3.4 MODBUS communication function
MODBUS protocol is a communication protocol developed by Modicon. It is
used to communicate with a PC or PLC.
Register content is read and written by this communication protocol.
This communication has the following features.
・Controls run/stop.
・Sets and reads the circulating fluid set temperature.
・Reads the circulating fluid discharge temperature.
・Reads the condition of the product.
・Reads the alarm generating condition of the product.
Refer to “3.13 Register Map” for the register of the product.
3.5 Precautions for communication
3.5.1 Precautions after wiring and before communication
○Check or set the each communication setting by the operation display
panel.
・The communication specification shall be the customer’s communication
standard.
・The communication mode shall be the SERIAL mode. (When serial mode is
activated, this mode is selected. Refer to Chapter 3.13.11)
Other modes can perform reading, but only SERIAL mode can perform
writing.
○Check or set the communication parameters using the operation display
panel.
Check or set the communication speed so that the product synchronizes with
the host computer (master) prepared by the customer.
○Check the slave address by the operation display panel.
No response is returned when a request message is sent from a slave
address other than those set in the product.
3.5.2 Precautions for communicating
○Allow a suitable interval between requests.
To send request messages in series, wait for 100 msec. or longer after
receiving a response message from the product before sending the next
message.
○Retry (resend request message)
.
The response may not be returned due to noise. If no message is returned
1sec. after sending a request message, resend the request message.
○If necessary send a read request message to check if it was written
correctly.
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