KB3920 extends the channels of Interrupt Controller in the original 8051 to 24 channels supporting internal peripheral devices. The Serial port use SCON2 to achieve high speed serial transmission rate up to 115200 bps. The two 16-bit timers are basically the same as that in the standard 8051’s, except when SCON2 is used to generate high-speed baud rate. Under such circumstances the 2 timers will not be used for baud-rate generation but for other purposes. The 8051 uses MOVX and MOVC instructions to read or write KB3920 peripherals, i.e., EC, SMBus, GPIO, GPWU, KBC, IKB, GPT, PWM, PS2, XBI, LPC, XRAM…etc.