Automatic response function
The automatic response function is a function that the RJ71EN71 or RnENCPU (network part) automatically executes a
necessary processing based on the function code in a request message received from a MODBUS/TCP master device and
sends the response message to the MODBUS/TCP master device.
A program is not required on the RJ71EN71 or RnENCPU (network part) side to send the response message.
The automatic response function uses the MODBUS device assignment function. For details, refer to the following.
Page 109 MODBUS device assignment function
For the function codes supported by the RJ71EN71 and RnENCPU (network part), refer to the following.
MELSEiQ-R MODBUS/TCP Reference Manual
A request message is received.
The function code is checked.
The requested processing is executed.
The response message is sent.
Set the automatic response function in "External Device Configuration" under "Basic Settings". (Page 244 External
Select "MODBUS/TCP Connection Module" in "Module List", and drag it to "List of devices" or "Device map area".
Set "Port No." and "#Existence Confirmation".
When multiple devices are set in "MODBUS/TCP Connection Module", set the same value to "Port No." of all devices.
Select [Close with Reflecting the Setting] to finish the external device configuration settings.
After the initial processing of the RJ71EN71 and RnENCPU (network part) completes, the port automatically opens according
to the parameter settings. The port automatically closes when the station on which the RJ71EN71 and RnENCPU (network
part) are mounted is turned off or reset.
When a dedicated instruction and the automatic communication function are simultaneously used with the QJ71MT91 set as
the MODBUS/TCP master device, set two devices to "MODBUS/TCP Connection Module" in "External Device Configuration".
For dedicated instructions and the automatic communication function of the QJ71MT91, refer to the following.
/TCP Interface Module User's Manual
1.7 Communications Using MODBUS/TCP
Request message (function code)
TCP master device