AT89C55 8-Bit Microcontroller with 20K Bytes Flash

Overview

The AT89C55 is a low-power, high-performance CMOS 8-bit microcontroller featuring 20KB of Flash programmable and erasable read-only memory. Manufactured using Atmel's high-density nonvolatile memory technology, this device maintains full compatibility with the industry-standard 80C51 instruction set and pinout configuration. The integrated Flash memory enables in-system reprogramming capability through conventional nonvolatile memory programmers or directly in the target application.

This microcontroller combines an efficient 8-bit CPU with substantial on-chip Flash memory, creating a versatile embedded control solution that offers exceptional flexibility and cost-effectiveness for a wide range of applications. The architecture supports static operation down to zero frequency, making it suitable for low-power implementations.

Key Features

• MCS-51™ Compatibility: Fully compatible with industry-standard 80C51 products
• Memory Configuration:
  • 20KB of in-system reprogrammable Flash memory (1,000 write/erase cycles endurance)
  • 256 x 8-bit internal RAM
• Performance Characteristics:
  • Fully static operation: 0 Hz to 33 MHz clock frequency
  • Three-level program memory lock for security
• I/O Capabilities: 32 programmable I/O lines
• Timing Resources: Three 16-bit timer/counters
• Interrupt System: Eight interrupt sources with six-vector two-level architecture
• Power Management:
  • Idle mode (CPU stopped while peripherals remain active)
  • Power-down mode (ultra-low power consumption)
• Communication Interface: Full-duplex serial port
• On-chip Peripherals: Integrated oscillator and clock circuitry

Applications

The AT89C55 is particularly well-suited for embedded control applications requiring:

• Industrial control systems
• Automotive electronics
• Consumer appliances
• Telecommunications equipment
• Medical devices
• Security systems
• Smart sensors and instrumentation
• Power management systems

Its combination of substantial Flash memory, versatile I/O capabilities, and power-saving modes makes it ideal for applications demanding both performance and energy efficiency.

Electrical Characteristics

Absolute Maximum Ratings

• Operating Temperature: -40°C to +85°C
• Storage Temperature: -65°C to +150°C
• Voltage on Any Pin Relative to Ground: -0.5V to V_CC+0.5V
• Maximum Operating Voltage: 6.6V
• DC Output Current: 15mA per I/O pin

Recommended Operating Conditions

• Supply Voltage (V_CC): 4.0V to 5.5V
• Operating Frequency: 0Hz to 33MHz
• Input Low Voltage (V_IL): -0.5V to 0.2V_CC-0.1V
• Input High Voltage (V_IH): 0.2V_CC+0.9V to V_CC+0.5V

Power Consumption

• Active Mode (12MHz): 25mA typical
• Idle Mode (12MHz): 6.5mA typical
• Power-down Mode: 50μA typical

Package Information

Available Package Types

• PLCC (Plastic Leaded Chip Carrier): 44-lead package
• PQFP (Plastic Quad Flat Pack): 44-lead package
• TQFP (Thin Quad Flat Pack): 44-lead package

Pin Configuration

The AT89C55 maintains the standard 80C51 pinout configuration with the following key pin functions:

• Port 0 (P0.0-P0.7): 8-bit open-drain bidirectional I/O port
• Port 1 (P1.0-P1.7): 8-bit bidirectional I/O port with internal pull-ups
• Port 2 (P2.0-P2.7): 8-bit bidirectional I/O port with internal pull-ups
• Port 3 (P3.0-P3.7): 8-bit bidirectional I/O port with alternate functions
• RST: Reset input (active high)
• ALE/PROG: Address Latch Enable/programming pulse input
• PSEN: Program Store Enable (read strobe for external program memory)
• EA/VPP: External Access Enable/programming voltage input
• XTAL1/XTAL2: Crystal oscillator connections

Architectural Overview

The AT89C55 features a modified Harvard architecture with the following key functional blocks:

• Central Processing Unit (CPU): 8-bit architecture with optimized instruction set
• Program Memory: 20KB Flash organized as 16K + 4K with separate lock bits
• Data Memory: 256 bytes internal RAM (128 bytes standard + 128 bytes extended)
• Special Function Registers (SFRs): 128-byte space for peripheral control
• Timers/Counters: Three 16-bit timers (Timer 0, Timer 1, and Timer 2)
• Serial Port: Full-duplex UART with dedicated baud rate generator
• Interrupt System: Six interrupt sources with two priority levels

Development Support

The AT89C55 is supported by a comprehensive development ecosystem including:

• In-circuit emulators and debuggers
• C and assembly language compilers
• Flash programming tools
• Evaluation boards
• Software libraries

The device's compatibility with the 80C51 architecture ensures access to a wide range of existing development tools and code resources.

Conclusion

The AT89C55 represents a powerful, flexible solution for embedded control applications, combining substantial Flash memory capacity with the proven 80C51 architecture. Its low-power capabilities, comprehensive peripheral set, and in-system reprogrammability make it particularly suitable for applications requiring field upgrades or power-sensitive operation. The device's static design allows for clock stopping without data loss, while its three memory lock bits provide intellectual property protection.