AT80C51RD2-RLRUM [Microchip]

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, they feature a Programmable Counter Array, 1024 bytes of Expanded RAM (XRAM), a Hardware Watchdog Timer, a Keyboard Interface, an Enhanced UART (EUART), and a speed improvement mechanism (X2 mode). They include software-selectable power reduction modes and an 8-bit clock prescaler. The devices operate at 10 to 40 MHz and offer 64K program and data memory spaces.