a digital thermometer using the at89c2051 microcontroller-外文文献.doc

A Digital Thermometer Using the AT89C2051 Microcontroller Introduction The system presented in this applicationnote implements a simple digital thermometerthat includes a built-in LCD and RS-485 communication port . It is designed around Atmel’s AT89C2051 processor, a DS1620 digital thermometer/thermostat from Dallas Semiconductor,a small 8 X 2 LED backlit LCD, and an RS485 line interface. The system,shown in Figure 1, can be used as the basis for developing custom solutions for networked and stand alone data collection and control equipment. It can be centrally powered due to its low current requirement and its small size allows it to be placed almost anywhere. Software 1．AT89C2051 Description The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2K bytes of Flash programmable and erasable read-only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a power-ful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89C2051 provides the following standard features: 2K bytes of Flash, 128 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In addition, the AT89C2051 is designed with static logic for opera-tion 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 hardware reset. Features ? Compatible with MCS?-51Products ? 2K Bytes of Reprogrammable Flash Me