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MELSEC-Q
7 DATA COMMUNICATIONS USING BIDIRECTIONAL PROTOCOL
7.2.4 How to detect transmission errors
This section explains how to detect errors that may occur when sending data to the
external device.
The following items are considered as the primary causes of errors that may occur
during data transmission.
Cause of transmission error Reference section
A transmission error occurred because of noise. —
A timeout occurred for the no-reception monitoring time (timer 0). Section 6.1
A timeout occurred for the response monitoring time (timer 1). Section 6.2
A timeout occurred for the transmission monitoring time (timer 2) Section 6.3
Data that could not be converted with the ASCII-BIN conversion was detected.
User's Manual
(Application)
Chapter 13
Designated the transmission data count that exceeded the transmission area size. Section 7.2.2
Simultaneous transmissions occurred. Section 7.3
(1) Confirmation using the sequence program
(a) Detecting a transmission error
1) The following device and input signal turn ON.
• BIDOUT instruction complete device + 1
• ERR LED ON signal (XE/XF)
2) The transmission error code can be checked using the BIDOUT
instruction control data ((S1) + 1).
Or, it can be checked by reading the data transmission result storage
area in the buffer memory (addresses 257
H
/267
H
).
For details on how to check the error code contents and corrective
actions, see Chapter 10.
(b) How to turn off the ERR LED and clear the error code (see Section 10.1.2)
1) To turn off only the ERR LED, write a "1" to the LED OFF request area
(addresses 0
H
/1
H
) in the buffer memory.
2) To turn off the ERR LED and clear the error code, turn ON the ERR LED
OFF request output signal (YE/YF).
(Example) To perform the ERR LED OFF and the error code clear on
the CH1 side:
Read command