Atmel AT89 Series Microcontrollers
The **Atmel AT89** series is an enhanced variant of the classic Intel 8051 microcontroller, featuring Flash memory instead of the original Mask ROM or EPROM. These microcontrollers are widely used in industrial, embedded, and automation applications due to their reliability and ease of programming.
Key Features
- 8-bit microcontroller based on the **MCS-51 architecture**
- Up to **64 KB Flash memory** for program storage
- Up to **256 bytes of internal RAM**, plus external memory support
- Multiple **I/O ports (32-bit)** with programmable pin configurations
- Three **16-bit timers/counters**
- **UART (Serial Communication)** with full-duplex support
- **Interrupt System** with multiple priority levels
- **Watchdog Timer (WDT)** for system stability
- On-chip **Analog Comparator** (in select models)
- Supports both **Internal and External Oscillators**
Memory Architecture
The AT89 series maintains the Harvard architecture of the 8051, separating program and data memory:
- Program Memory (Flash) - Up to **64 KB**
- Internal Data Memory (RAM) - **128 or 256 bytes**
- External RAM support up to **64 KB**
- EEPROM (available in some models) for **non-volatile storage**
Peripherals & I/O Functions
The AT89 series integrates various peripherals:
- GPIO (General-Purpose Input/Output) - **Up to 32 pins**
- Timers - Three **16-bit timers/counters** for event counting and delays
- Serial Communication - **Full-duplex UART** supporting multiple baud rates
- External Interrupts - **Two external interrupt sources**
- Watchdog Timer (WDT) - Prevents system crashes by resetting on failures
- Analog Comparator - Available on selected variants
Common Variants in the AT89 Family
| Model |
Flash (KB) |
RAM (Bytes) |
EEPROM |
I/O Pins |
Timers |
Special Features |
| AT89C51 |
4 |
128 |
No |
32 |
3 |
Standard 8051 with Flash |
| AT89C52 |
8 |
256 |
No |
32 |
3 |
Enhanced 8051 with extra RAM |
| AT89S51 |
4 |
128 |
No |
32 |
3 |
Supports SPI programming |
| AT89S52 |
8 |
256 |
No |
32 |
3 |
Faster processing speed |
| AT89LP52 |
8 |
256 |
Yes |
32 |
3 |
Low-power version, EEPROM included |
Programming and Development
The AT89 series microcontrollers are programmed using **assembly language or C**. Common development tools include:
- **Keil uVision** - Popular for embedded C development
- **SDCC (Small Device C Compiler)** - Open-source alternative
- **Atmel Studio** - Official IDE for Atmel devices
- **Flash Magic** - Used for ISP (In-System Programming)
Applications
Due to their flexibility and ease of use, AT89 microcontrollers are used in:
- Industrial automation & process control
- Embedded systems in **consumer electronics**
- Data acquisition & logging
- Security systems (RFID, biometric scanners)
- Simple robotics & motor control
- Automotive applications
Conclusion
The Atmel AT89 series offers a **reliable** and **affordable** solution for embedded systems. Its compatibility with the 8051 architecture makes it an easy upgrade path for legacy applications, while the integration of Flash memory and improved peripherals makes it useful in modern designs.