Melsec PLC’s from Mitsubishi can be connected to PC’s running Medoc programming software using various cables. Each different I/O module uses a different pin assignment.
Not all Mitsubishi PLCs can be connected directly to a programming PC. The signal levels of the A series CPU units are not RS232 compatible and must be converted with a SC-02N or SC-05 converter. The serial cable layout to connect this converter to a PC is shown in this diagram.
PC to Mitsubishi SC-02N/SC-05 adapter cable
If more than one serial port is necessary on an A series melsec PLC, the AJ71C24 or AJ71C21 serial communication modules can be plugged into the system. These modules provide RS232 compatible serial ports, so no signal conversion is necessary to connect these modules with a PC. Both modules are equipped with a DB25 connector. The cable layout for these two modules is shown below.
PC to Mitsubishi AJ71C24 serial programming cable
PC to Mitsubishi AJ71C21 serial programming cable
The A1SJ71C24-R2 can also be used to connect computers and devices to a melsec series A PLC. This plug-in module contains two serial ports, each with a DB9 connector. The wiring layout is in fact identical to the RS232 null modem cable with loopback handshaking.
PC to Mitsubishi A1SJ71C24-R2 serial programming cable