Microcontroller › 8051 › More accurate schematic and circuit diagram for electronic password door locking system › i hv not seen the circuit but
i hv not seen the circuit but i will say you can connect keypad in two ways
in simple way you can directly connect rows and columns of keys to IO pins of device. no need to connect ground or supply.
in another way if you want to source or sink current when key is pressed throuch external source, you have to connect Vcc to keys