Hoping that the keyboard would work, I did some research and found out that the last unknown pin was -12V. Since it is the RS232C protocol, it naturally requires -12V.
So, all the pin-outs were clear and ready to communicate with the keyboard. However, making the -12V is a pain. I ended up connecting the RxD and TxD of the HD6303 to a USB serial to see if I could receive data from the keyboard.
I set the communication speed to 38400 Baud (stop-bits and parity are still unknown). I know that the data to be sent is scancode, so I can make it work.
