AT80C51RD2 microcontrollers are high-performance versions of the 80C51 8-bit microcontrollers. The microcontrollers retain all the features of the Atmel 80C52, with 256 bytes of internal RAM, a 7-source 4-level interrupt controller, and three timers/counters. Additionally, microcontrollers feature a Programmable Counter Array, a 1024-byte XRAM, a Hardware Monitor Timer, a Keyboard Interface, a more versatile serial channel (EUART) that facilitates multiprocessor communication, and a speed improvement mechanism (X2 mode).