Dobb's Journal July 1997: Atmel's AT89C2051 Microcontroller Dhananjay is a scientific officer for the instrumentation laboratory at the Inter-University Centre for Astronomy & Astrophysics (IUCAA) in Pune, India. He can be contacted at The Atmel AT89C2051 is a low-power, high-performance 8-bit microcontroller compatible with the MSC-51 instruction set and object code. The 20-pin AT89C2051, with its many hardware features, is especially attractive to 8051 developers because it is compatible with the 8051 and similar devices, and can reduce board space, components, and cost. In an application comprised of EPROM, address latch, an 8051, and other associated components, for instance, the 8051 offers enough on-chip digital I/O that additional external I/O components may not be required. In a similar AT89C2051-based system, however, a single AT89C2051 can replace the EPROM, latch, and 8051, providing the system software is limited to 2 KB. The AT89C2051 features: • 2 KB of on-chip Flash program memory. • 128 bytes of internal RAM.

Atmel AT89c2051, AT89c1051 and AT89c4051 are compatible with Intel 8051 Industry Standard. A lot of freeware is available (Assembler, C, Debugger and mountains of ready to use software applications on the internet). 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.

• Fully static operation: 0 Hz to 24 MHz. • Instruction compatible with MCS-51. • 15 I/O lines.

• Full duplex programmable serial port. • Two 16-bit programmable timers. • On-chip analog comparator. • Low-power and power-down modes. Podelki applikacii pro kazahstan live. • Wide operating voltages: 2.7 V to 6 V. Metal gear solid psx rip.

• 20-pin DIP/SOIC package. The use of static memory allows the device to be operated at zero frequency. It also affords two software-selectable save-power modes. Idle mode stops the CPU, retaining the contents of the internal RAM, allowing the timer/counter, interrupt system, and serial ports to function normally. Power-down mode saves the RAM contents but freezes the oscillator, disabling all other activity until the next hardware reset. The amount of PEROM (programmable and erasable read-only memory) available on the AT89C2051 is sufficient for most applications, including use in portable instruments, supervisory-control applications, autonomous robots, and more. Use as controllers in portable instruments is further simplified by the low power consumption and wide operating voltage range.

The AT89C2051 allows 15 bits of I/O, configured as 8 bits on Port1 and 7 bits on Port3. Port1 and Port3 are compatible to the P1 and P3 on an 8051 (except Port1.0 and Port1.1).

Port1 pins P1.0 and P1.1 require external pullups. P1.0 and P1.1 pins also serve as inputs to an on-chip analog comparator (+ve and -ve inputs, respectively). Port1 output buffers have a 20 mA sink current capacity and can drive LEDs directly. By writing ones to the Port1 bits, they can be used as input bits.