Multiplexer-based C51 MCU status display circuit schematics

shown below, AT89S51 MCU P1.0 - P1.3 pick four light-emitting diodes L1 - L4, P1.4 - P1.7 pick up four switches K1 - K4, programming will reflect the state of the switch to the light-emitting diodes . (The switch is closed, the corresponding lights, switch off, the corresponding light off).

1. The "SCM system" area of P1.0 - P1.3 with a wire connected to the "Eight LEDs indicate module" area of L1 - L4 port;
2. The "SCM system" area of P1.4 - P1.7 with a wire connected to the "four toggle switch" area of K1 - K4 port.