8051 Delivers RISC Performance with CISC Technology


Building on a Legacy of Leadership

Atmel has a long tradition of innovation in Flash microcontroller technology. We introduced the first 8-bit Flash microcontroller in 1993, based on the classic 8051 core. The on-chip Flash memory retained its contents even after power was turned off, and was electrically erasable and programmable. Atmel’s 8051 8-bit microcontrollers were the industry’s first Flash based microcontrollers featuring In-System Programming. Atmel also pioneered In-Application Programming in its Flash microcontrollers to enable remote upgrades.


Single-Cycle AT89LP Family

The Atmel AT89LP family is based on a low power, high performance 8-bit Single-Cycle 8051 core. The classic 8051 CPU requires 12 clock cycles for every byte fetch, while the new AT89LP CPU requires only one clock cycle. The AT89LP family instructions need only 1 to 4 clock cycles to complete, providing up to 12 times greater throughput than the classic 8051. Seventy percent of the instructions execute in the same number of clock cycles as the number of bytes to be fetched.

The AT89LP core also delivers powerful performance, with up to 20 million instructions per second (MIPS) throughput at 20 MHz clock frequency—more than 10 times the throughput of the original 8051. Conversely, at the same MIPS throughput as the classic 8051, the new AT89LP core runs at a much lower clock frequency, greatly reducing power consumption. This efficient design lets AT89LP devices operate down to 2.0V supply voltage.

The Single-Cycle AT89LP family of devices offer enhanced features accessible through instructions that are 100 percent binary compatible with the traditional 8051 instruction set. The Special Function Register (SFR) addresses and bit assignments are compatible with current Atmel 8051 microcontrollers. The AT89LP core also features several architectural improvements that make it an excellent fit for low power, high performance applications.

  • System Clock: The CPU clock frequency equals the XTAL1 frequency. The crystal oscillator no longer needs division by two.
  • CPU: The CPU fetches one byte from code memory every clock cycle, instead of every twelve clock cycles. This greatly increases the throughput of the CPU and reduces the power consumption. As a result, the CPU can execute instructions in one to four clock cyles, rather than 12 to 48 clock cycles.
  • Timer/Counters: The Timer/Counters in Atmel AT89LP devices are enhanced in Mode 0 as a variable 9- to 16-bit timer/counter and in Mode 1 as a 16-bit auto-reload timer/counter. In the new architecture the Timer/Counters increment at a rate of once per clock cycle. This compares to once every 12 clocks in the classic 8051.
  • Serial Port: The AT89LP UART supports Automatic Address Recognition and Frame Error Detection. Its baud rate in Mode 0 is 1/2 the clock frequency, compared to 1/12 the clock frequency in the classic 8051.
  • I/O Ports: The I/O ports may be configured in four different modes: input-only (tristated), full CMOS output, open-drain output and quasi-bidirectional (classic 8051).
  • Reset: The RST pin is active-low as compared with the active-high reset in the classic 8051, resulting in reduced latch-up susceptibility.

A Rich Level of System Integration

Atmel AT89LP microcontrollers are built around an enhanced 8051 CPU, and are fully binary compatible with the industry standard MCS®51 instruction set. The CPU employs a simple two-stage pipeline to fetch and execute one instruction byte per clock cycle, allowing up to 1 MIPS per MHz of system frequency.

The enhanced CPU is paired with on-chip RAM and a range of integrated peripherals, including at least two 16-bit timers, multi-phasic pulse width modulator (two to four phases), an enhanced UART, a master/slave SPI, debounced analog comparators, 10-bit analog-to-digital converter, watchdog timer, and pin-based configurable interrupts. Select higher-end derivatives also support DSP extensions.

The devices also include system functions such as Power-on Reset, Brown-out Detection, and an on-chip high precision RC Oscillator. The devices include 2KB up to 256KB of In-System Programmable Flash memory for code storage and up to 64KB of on-chip Flash data memory. The high level of system integration on AT89LP devices helps reduce system cost and power consumption, while accelerating time-to-market.


Rich Performance and Ease of Use

Atmel AT89LP family devices are cost-effective 8-bit microcontrollers that are ideal for applications requiring low power and high performance. These microcontrollers reduce system cost with a variety of on-chip features to enable faster time-to-market. The AT89LP family is well-suited for power management, white goods, and universal remote control applications, and delivers greater system-level integration. With the new AT89LP devices, system designers can enjoy up to 80 percent decrease in power consumption compared to classic 8051 microcontrollers at the same MIPS performance level. This efficiency also significantly improves EMC characteristics.

Binary compatibility with the standard 8051-instruction set allows upward migration from multi-clock cycle 8051 cores to the higher performance AT89LP-series. Atmel’s Single-Cycle AT89LP Flash Microcontrollers are easy to use, and offer a rich and powerful CISC instruction set at RISC performance.

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