AT80C51RD2-3CSUM 8-bit MCS-8051 microcontroller, ROMless, 40 MHz, DIP-40

The AT80C51RD2 microcontrollers are high-performance versions of the 80C51 8-bit microcontrollers. They retain all the features of the Atmel 80C52 with 256 bytes of internal RAM, a 7-source interrupt controller with 4 levels, and three timers/counters. In addition, the microcontrollers feature a programmable timer array, 1024-byte XRAM, a hardware watchdog timer, a keyboard interface, a more versatile serial channel that facilitates multiprocessor communication (EUART), and a speed enhancement mechanism (X2 mode). The microcontrollers feature 2 software-selectable modes for reduced activity and a 8-bit clock prescaler for further reduction of power consumption. In idle mode, the CPU is frozen while the peripherals and the interrupt system are still in operation. In power-down mode, RAM is stored and all other functions are overridden. RAM: 256 bytes II/O pins: 32 Timer: 3