MODBUS Communication
4
TI 12A01F01-62EN
1.4 MODBUS communication
The following must be cared when master devices other than FieldMate are used.
l MODBUS response timing
IR (Input Register) response to IR Read request within 50 ms after FLXA402 receives the
message. To the other request, FLXA402 replies within 100 ms after it receives the request.
Another request must be sent at least 100 ms after the last response was received from
FLXA402.
<50ms >100ms <100ms
User
FLXA402
HR RequestIR Request
IR
：
Input Register
HR
：
Holding Register
HR ResponseIR Response
l Input Register renewal cycle
Process value sent in Input Register is renewed every 500 ms. It is better to Read the process
value every 500 ms.
l How to change the setting
• Turn ON Coil register 31 to grant access authority
• Change the Coil/Holding register
• Turn OFF the coil to restrict the access again after the renewal completes.
NOTE
Even if you have no access authority, you can register WASH Start/Stop, WASH Recovery stop.
For other parameters, follow the procedure above. If you try to write the parameters without
access, an error response (Error code 03) is replied.
NOTE
When FLXA402 has access to measured data, you cannot set devices by using HMI or other
devices on the network. Even after FLXA402 loses access, this situation remains unchanged for
3 seconds.
NOTE
When no message comes for 30 seconds from MODBUS master which has access, the access
turns OFF automatically.
Apr. 19, 2019-00
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