Reception Monitoring Time (Timer 0) Setting; C24 Operation By No Reception Monitoring Time (Timer 0) - Mitsubishi Electric MELSEC iQ-R Series User Manual

10.1
No-reception Monitoring Time (timer 0) Setting
The no-reception monitoring time (timer 0) is a monitoring time for clearing the state of C24 when it is placed into the data
receive wait state by trouble on the target device side.
C24 monitors the reception interval in byte units at the start of data reception from the target device and ends monitoring when
the preset last data is received, and it repeats this operation.
The following explains the no-reception monitoring time (timer 0) operation.
Target device Data 1
CPU module
One byte is always handled as 12 bits in the no-reception monitoring time (timer 0), regardless of the transmission setting.
When the no-reception monitoring time (timer 0) is changed by a program, perform any of the following to enable the changed
value.
• Mode switching (Page 377 SWITCHING THE MODE AFTER STARTING)
• UINI instruction (MELSEC iQ-R Programming Manual (Instructions, Standard functions/Function blocks))
• Programmable controller CPU information clear (Page 455 How to Clear Programmable Controller CPU Information)

C24 operation by no reception monitoring time (timer 0)

C24 monitors the reception interval in byte units and returns the elapsed time to 0 each time one byte is received.
At time-out, C24 performs the following processing.
Data communication using the MC protocol
• C24 stores the error code to the 'MC protocol send error code' (Un\G602/618) for the target interface side.
• C24 transmits a NAK message to the target device and waits to receive the next command message.
Data communications using the nonprocedural protocol (Method 0)
■Data communications not using user frames
• C24 retrieves the received data up to time-out to C24.
• C24 stores the error code to the 'Data reception result' (Un\G600/616) for the target interface and turns ON the 'CH
reception abnormal detection' (X4, XB), and waits to receive the next data.
Ex.
Receiving by the receive end code (Receive end code: CR + LF (0D0AH))
When the LF is not received within the set time for timer 0 after reception of the CR, the received data up to the CR is stored
in the receive data storage area of the buffer memory and the reception abnormal detection signal to the CPU module turns
ON.
Target device
C24
Reception abnormal detection signal
(X4/XB)
*1 CR is treated as 1 byte of data included in the message.
10 CHANGING DATA COMMUNICATION MONITORING TIME
228
10.1 No-reception Monitoring Time (timer 0) Setting
Data 2 Data n-1
Monitoring
time
1 byte
Data n
Data receive interval
(depends on the transmission rate, etc.)
Elapsed time reset
Timer 0
Set time
CR
(*1)