Carrier Detection Flag [M8404 And M8424] - Mitsubishi Electric FX3U-232-BD User Manual

FX Series PLC User's Manual - Data Communication Edition
Non-Protocol Communication (RS/RS2 Instruction)

12.4.5 Carrier detection flag [M8404 and M8424]

These devices turn ON/OFF in synchronization with the CD (DCD) signal.
1. Detailed contents
The CD (DCD) signal (channel receiving carrier detection) turns ON when the modem line is established.
When communication port ch1 is used, M8404 turns ON/OFF.
When communication port ch2 is used, M8424 turns ON/OFF.
While the carrier detection flag is OFF, the dial number can be sent.
While the carrier detection flag is ON, data can be sent and received.
12.4.6 Data set ready (DSR) flag [M8405 and M8425]
These devices turn ON/OFF in synchronization with the DR (DSR) signal.
1. Detailed contents
The state of DR (DSR) signal can be checked when executing RS2 instruction.
When communicating port ch1 is used, M8405 turns ON/OFF.
When communication port ch2 is used, M8425 turns ON/OFF.
The images of M8405 and M8425 are updated during END processing.
12.4.7 Time-out check flag [M8379, M8409 and M8429]
These devices turn ON when data receiving is suspended, and the next set of receive data is not given within
the time set by the time-out time setting device.
1. Detailed contents
These devices turn ON when data receiving is suspended and the next set of receive data is not given within
the time set by the time-out time setting device. The receiving complete flag also turns ON.
When communication port ch0 is used, M8379 turns ON.
When communication port ch1 is used, M8409 turns ON.
When communication port ch2 is used, M8429 turns ON.
The time-out check flag turns OFF when the PLC waits to receive.
Using this function, the PLC can receive data from equipment where the amount of send data varies without
the terminators.
Receiving
Time-out check flag
M8409
Receiving complete
M8403
Receive data is
suspended.
Data
D8409
 10 ms
ON
ON
12.4 Details of Related Devices (RS2 Instruction)
Set to OFF in sequence program.
12 Related Data
A
B
C
D
E
F
G
H
I
Apx.A
F-99