Mitsubishi MELSEC LJ71C24, Руководство пользователя

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15 TROUBLESHOOTING
15.1.3 Reading the RS-232 control signal status
This section explains how to read the control signal status stored in the buffer memory
during communication using RS-232 interface.
When using GX Works2, check in the "Intelligent Function Module Monitor" screen.
(Refer to the GX Works2 Version1 Operating Manual (Intelligent Function Module).)
When a transmission problem occurs, read operation is executed to check the signal
on/off status of the RS-232 interface.
(1) RS-232 control signal status (address: 254
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The RS-232 control signal status is stored as follows.
REMARKS
(1) For details on signals for RS-232, refer to Section 6.2.1.
(2) Signals output from the C24 side (RS(RTS) and ER(DTR)) are controlled by the
operating system (OS) of the C24.
They cannot be directly controlled by the sequence program.
(3) There is a maximum delay of 100 ms in signal status stored in the buffer
memory above.
(2) Example of a program that reads from RS-232 control signal status
(address: 254
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The following shows an example of a program that reads the RS-232 control
signal status.
(input/output signals X/Y00 to X/Y1F of the C24)
Example of FROM instruction