80C51 microcontrollers are high performance versions of the 80C51 8-bit microcontrollers. The microcontrollers retain all features of the Atmel 80C52 with 256 bytes of internal RAM, a 7-source 4-level interrupt controller and three timer/counters. In addition, the microcontrollers have a Programmable Counter Array, an XRAM of 1024 byte, a Hardware Watchdog Timer, a Keyboard Interface, a more versatile serial channel that facilitates multiprocessor communication (EUART) and a speed improvement mechanism (X2 mode).
The microcontrollers have 2 software-selectable modes of reduced activity and 8 bit clock prescaler for further reduction in power consumption. In Idle mode, the CPU is frozen while the peripherals and the interrupt system are still operating. In the Power-down mode, the RAM is saved and all other functions are inoperative.