Chapter 23 Rs-422/485 Interface Echo Back Enable/Prohibit Specification - Mitsubishi Electric MELSEC iQ-R Series User Manual

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RS-422/485 INTERFACE ECHO BACK ENABLE/
PROHIBIT SPECIFICATION
This chapter explains the echo back enable/prohibit specification.
This function can be used for the both interfaces on RJ71C24(-R4).
The echo back function is a function that transmitted data is also sent to RDA or RDB on the host station when data
communication is performed through RS-458 (2-wire type) from RS-422/485 interface.
Whether to receive the returned data or not (discard) can be specified.
Data transmission
C24
SDA
SDB
RDA
RDB
Receives or not receive
(discards) the data.
Application
• Disabling the echo back will eliminate the processing to ignore unnecessary data, which has been programmed for
nonprocedural protocol communication.
• When the same message format is used for a request (command) and a response of the target device protocol during data
communication using the predefined protocol, disabling the echo back function can enable data communication with the
target device.
Setting method
• Setting by engineering tool
Set "Echo back enable/prohibit specification" to "Echo back enable" or "Echo back prohibit".
Navigation window  [Parameter]  [Module Information]  "Module Name"  [Module Parameter]  "Basic Settings"
 "Various control specification"
• Setting by a program
In the 'RS-422/485 interface echo back enable/prohibit specification' (Un\G290/450), store either of the following values.
(Default: 0)
Setting value
0: Echo back enable
1: Echo back prohibit
Precautions
The setting for the echo back enable/prohibit specification must be configured before sending data. Any setting changed
during transmission does not take effect.
Target device
SDA
SDB
RDA
RDB
Description
When C24 transmits data, it also receives the transmitted data with its own RDA or RDB.
When C24 transmits data, it does not receive the transmitted data with its own RDA or RDB. (The data is discarded.)
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