Datasheet

4235K–8051–05/08

AT89C51RD2/ED2

1. Description

AT89C51RD2/ED2 is high performance CMOS Flash version of the 80C51 CMOS single chip 8-

bit microcontroller. It contains a 64-Kbyte Flash memory block for code and for data.

The 64-Kbytes Flash memory can be programmed either in parallel mode or in serial mode with

the ISP capability or with software. The programming voltage is internally generated from the

standard V

pin.

The AT89C51RD2/ED2 retains all of the features of the Atmel 80C52 with 256 bytes of internal

RAM, a 9-source 4-level interrupt controller and three timer/counters. The AT89C51ED2 pro-

vides 2048 bytes of EEPROM for nonvolatile data storage.

In addition, the AT89C51RD2/ED2 has a Programmable Counter Array, an XRAM of 1792

bytes, a Hardware Watchdog Timer, SPI interface, Keyboard, a more versatile serial channel

that facilitates multiprocessor communication (EUART) and a speed improvement mechanism

(X2 Mode).

The fully static design of the AT89C51RD2/ED2 allows to reduce system power consumption by

bringing the clock frequency down to any value, including DC, without loss of data.

The AT89C51RD2/ED2 has 2 software-selectable modes of reduced activity and an 8-bit clock

prescaler for further reduction in power consumption. In the 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.

The added features of the AT89C51RD2/ED2 make it more powerful for applications that need

pulse width modulation, high speed I/O and counting capabilities such as alarms, motor control,

corded phones, and smart card readers.

Table 1-1. Memory Size and I/O Pins

Package Flash (Bytes) XRAM (Bytes) Total RAM (Bytes) I/O

PLCC44/VQFP44 64K 1792 2048 34

PLCC68/VQFP64 64K 1792 2048 50