Reception Error Detection And Check Methods; Receive Data Clear - Mitsubishi Electric MELSEC iQ-R Series User Manual

Reception error detection and check methods

The following explains how to detect and confirm errors that may occur when receiving data from target devices.
The following items are considered as the primary causes of errors that may occur during data reception.
Cause of reception error
A transmission error occurred due to noise.
A timeout occurred for the no-reception monitoring time (timer 0).
A timeout occurred for the send monitoring time (timer 2).
Data that could not be converted with the ASCII-BIN conversion was included.
The receive data length was too long to be stored in the receive area.
Simultaneous transmissions occurred.
Confirmation using a program
■Detecting a reception error
'CH Error occurrence' (XE/XF) turns ON.
■Confirming a reception error
Read the 'data reception result' (Un\G600/616), and check it.
For details on how to check the error code contents and corrective actions, refer to the following section.
Page 473 Error Code List
Confirmation using the module and Engineering tool
■Confirmation using the indicator LED
When C24 detects an error, including a transmission error, the ERR LED turns ON.
■Confirmation using Engineering tool
Read the 'data reception result' (Un\G600/616), and check the error code.
Considerations
• All of the received data for which an error was detected is ignored and a response message indicating an abnormal
completion (NAK message) is transmitted to the target device. The 'CH reception abnormal detection' (X4/XB) does not
turn ON.
When an error is detected during a message reception, C24 does not request the CPU module to read the received data.
• The receive area in the buffer memory will contain the data received normally just before the error occurrence. (Data will not
be rewritten.)

Receive data clear

Data communications using the bidirectional protocol must be performed after a response message is received in reply to the
preceding data transmission.
If C24 detects an error while receiving data, it transmits an NAK message (response message) to the target device after the
completion of the data reception and ignores the data being received when the error was detected.
Therefore, the received data does not have to be cleared.
Reference
MELSEC iQ-R Serial Communication Module User's
Manual (Startup)
Page 228 No-reception Monitoring Time (timer 0) Setting
Page 233 Send Monitoring Time (timer 2) Setting
Page 359 ASCII-BIN Conversion for Data Communicated
with Bidirectional Protocol
Page 88 Receive area, receive data arrangement and
contents
Page 104 Processing when Simultaneous Transmission is
Performed during Full-Duplex Communications
4 DATA COMMUNICATION USING BIDIRECTIONAL PROTOCOL
4.1 Receiving Data from Target Device
4
95