To establish an RS-232 connection with the Keyence KV-L21V PLC, you'll typically need the following components:

Step 1 : Connection details

SD - RxD

RG - TxD

SG - Gnd

Step 2 : Connect devive

1. Keyence KV-L21V PLC: This is the programmable logic controller you're connecting to.

2. RS-232 Communication Module: The KV-L21V PLC needs to be equipped with an RS-232 communication terminal.

3. RS-232 Cable: You'll need an RS-232 cable to physically connect the PLC to the device you're communicating with. T