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 eitherin parallel mode or in serial mode with the ISP capability or with software. The programming voltage is internally generated from the standard VCC 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 provides 2048 bytes of EEPROM for nonvolatile data storage.

FEATUREs
• 80C52 Compatible
   – 8051 Instruction Compatible
   – Six 8-bit I/O Ports (64 Pins or 68 Pins Versions)
   – Four 8-bit I/O Ports (44 Pins Version)
   – Three 16-bit Timer/Counters
   – 256 Bytes Scratch Pad RAM
   – 9 Interrupt Sources with 4 Priority Levels
• Integrated Power Monitor (POR/PFD) to Supervise Internal Power Supply
• ISP (In-System Programming) Using Standard VCC Power Supply
• 2048 Bytes Boot ROM Contains Low Level Flash Programming Routines and a Default Serial Loader
• High-speed Architecture
   – In Standard Mode:
• 40 MHz (Vcc 2.7V to 5.5V, both Internal and external code execution)
• 60 MHz (Vcc 4.5V to 5.5V and Internal Code execution only)
   – In X2 mode (6 Clocks/machine cycle)
• 20 MHz (Vcc 2.7V to 5.5V, both Internal and external code execution)
• 30 MHz (Vcc 4.5V to 5.5V and Internal Code execution only)
• 64K Bytes On-chip Flash Program/Data Memory
   – Byte and Page (128 Bytes) Erase and Write
   – 100k Write Cycles
• On-chip 1792 bytes Expanded RAM (XRAM)
   – Software Selectable Size (0, 256, 512, 768, 1024, 1792 Bytes)
   – 768 Bytes Selected at Reset for T89C51RD2 Compatibility
• On-chip 2048 Bytes EEPROM Block for Data Storage (AT89C51ED2 Only)
• 100K Write Cycles
• Dual Data Pointer
• Variable Length MOVX for Slow RAM/Peripherals
• Improved X2 Mode with Independent Selection for CPUand Each Peripheral
• Keyboard Interrupt Interface on Port 1
• SPI Interface (Master/Slave Mode)
• 8-bit Clock Prescaler
• 16-bit Programmable Counter Array
   – High Speed Output
   – Compare/Capture
   – Pulse Width Modulator
   – Watchdog Timer Capabilities
• Asynchronous Port Reset
• Full-duplex Enhanced UART with Dedicated Internal Baud Rate Generator
• Low EMI (Inhibit ALE)
• Hardware Watchdog Timer (One-time Enabled with Reset-Out), Power-off Flag
• Power Control Modes: Idle Mode, Power-down Mode
• Single Range Power Supply: 2.7V to 5.5V
• Industrial Temperature Range (-40 to +85°C)
• Packages: PLCC44, VQFP44, PLCC68, VQFP64