| Flash (Kbytes) | 20 |
| RAM (Bytes) | 256 |
| F.max (MHz) | 33 |
| Vcc (V) | 4.0-6.0 |
| I/O Pins | 32 |
| UART | 1 |
| 16-bit Timers | 3 |
| Watchdog | Yes |
| Pb-Free Packages | TQFP44 PDIP40 PLCC44 |
The AT89C55WD is a low-power, high-performance CMOS 8-bit microcontroller with 20K bytes of Flash programmable read only memory and 256 bytes of RAM. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry standard 80C51 and 80C52 instruction set and pinout. The on-chip Flash allows the program memory to be user programmed by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C55WD is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded controlapplications. The AT89C55WD provides the following standard features: 20K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector, two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C55WD is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset.
AT89C55WD是一个低电压，高性能CMOS 8位单片机，片内含20k bytes的可反复擦写的Flash只读程序存储器和256bytes的随机存取数据存储器（RAM），器件采用ATMEL公司的高密度、非易失性存储技术生产，兼容标准MCS-51指令系统，引脚兼容工业标准89C51和89C52芯片，采用通用编程方式，片内置通用8位中央处理器和Flash存储单元，内置功能强大的微处理器的AT89C52可为您提供许多高性价比的解决方案，适用于多数嵌入式应用系统。 AT89C55WD有40个引脚，32个外部双向输入/输出（I/O）端口，同时内含2个外中断口，2个16位可编程定时计数器,2个全双工串行通信口，2个读写口线，片内时钟电路，AT89C55WD采用两种软件控制其进入省电睡眠模式的静态逻辑工作闲置方式设计，可以用RAM、定时/计数器、串行口和外部中断唤醒睡眠状态而继续工作，在睡眠模式下，RAM被冻结，其他功能全部停止，直至下个外中断触发或硬件复位方可开始运行。特别是可反复擦写的Flash存储器可有效地降低开发成本。 AT89C55WD有具有PLCC、PDIP和TQFP三种封装形式，以适应不同产品的需求。
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| Speed (MHz) | Power Supply | Ordering Code | Package | Operation Range |
| 24 | 4.0V to 5.5V | AT89C55WD-24AU AT89C55WD-24JU AT89C55WD-24PU |
44A 44J 40P6 |
Industrial (-40°C to 85°C) |
