Electronic Design

8051 Keeps Plugging Away: Faster CPUs, Smaller Packages

The 8051 8-bit microcontroller just keeps plugging away, adding new peripherals, speed grades, and packaging. Among the latest advances is Dallas Semiconductor's 8051 implementation that delivers a 50x speedup over the original 12-clock instruction execution implementation.

Another 8051 vendor, Cygnal Integrated Products Inc., is fielding its own 20x speedup version of the 8051, coupled with a 12-bit ADC. And on the size front, Philips Semiconductor has introduced an even smaller 8051 package that targets deeply embedded applications.

8051s continue to be one of the more popular 8-bit microcontrollers. Thousands of engineers and programmers know its ISA intimately. Furthermore, there are tens of thousands of 8051 microcontroller programs and function libraries available that remain in use.

Because of its rather baroque addressing scheme, the 8051 may not be a super-easy architecture to use. But isn't a simple, 8-bit microcontroller with a restricted register easy to use? It has enough registers (2 banks of 16 registers) and addressing to handle mid-size applications.

A 50x Speedup
Dallas Semiconductor has made a good business of clean-room 8051 designs that push the 8051's speed limits. Its newest version, the DS89C420, delivers a 50-MIPS, which is a 50x speedup over the old 12-MHz, 12-stage 8051. Running at 50 MHz, it executes an 8051 instruction in a single clock cycle. Moreover, it offers a full redesign, one that implements the 8051 ISA with modern RISC-like technology. The 8051's sequential 12-stage execution model was transformed into a 4-stage pipelined architecture that delivers apparent 1-cycle instruction execution.

An ultra-high-speed microcontroller, the DS89C420 is 100% pin- and instruction-set compatible with the 8051. When it was first designed, instruction execution was cut to 4 clocks instead of 12. This redesign decreases that amount to 1 clock cycle (pipelined). In addition to being 80C52-compatible, the 8051 features 4 bidirectional I/O ports, a 16-KB flash memory, and a 256-byte scratchpad RAM. It also offers 3 16-bit timers and a 1-KB data SRAM for MOVX operations. Peripherals include 2 full-duplex serial ports, a programmable watchdog timer, and 13 interrupts (6 external).

Now in full production, the DS879C42 is priced from $10.10 in 25,000-unit lots. Packages include 40-pin PDIPs, 44-pin PLCCs, and 44-pin TQFPs. The chip is available in two temperature grades: 0°C to 70°C and −40°C to 85°C.

An 8051 In A 20-Pin TSSOP
Philips Semiconductor made its reputation in the 8051 world with its small packages. The company's most recent variation comprises the 87LPC762 and the 87LPC764. This package crams a full 8051 with peripherals into a 20-pin TSSOP that's just 4.4 by 6.5 by 1.1 mm. It cuts the 8051 packaging footprint by 1.3.

The 87LPC762/764 runs at up to 20 MHz and uses a 6-clock core (6 clocks per instruction, not 12). It has 2 timer-counters, an I2C serial bus, a UART serial port, and 2 KB or 4 KB of OTP memory, respectively. Plus, both microcontrollers support power-on reset and a keypad interrupt. They support 12 interrupts (3 are external).

In 10,000-unit quantities, the 87LPC762 sell for $1.05 each, while the 764 is priced at $1.15 per unit. Both are packaged in TSSOPs.

A 20-MIPS 8051 Plus A 12-Bit ADC
Dallas Semiconductor is not the only 8051 vendor to re-implement the venerable 8-bitter for speed. Cygnal's engineers redesigned the 8051 as well, getting a 1-clock cycle (pipelined) instruction execution. Its 8051 implementation runs at 20 MHz and delivers 20 MIPS peak.

Cygnal's C8051Fxx is a family of 8051-based mixed-signal, flash memory processors. The C8051F002 boasts a 20-MHz, 20-MIPS 8051 CPU with 32 KB of in-system programmable flash memory and 256 B of SRAM. Peripherals incorporate a UART serial port, an SMBus port, 4 8051 timers, and a 5-channel programmable counter array. Among the mixed-signal peripherals are a 12-bit ADC, 2 12-bit digital-to-analog converters, and a voltage comparator.

Available in 1000-unit lots, the C8051F02 is priced at $12.13. The C8051F000DK development kit costs $99.

See associated figure

Dallas Semiconductor, 4401 Beltwood Pkwy., Dallas, TX 75244; (972) 371-4000; www.dalsemi.com.

Philips Semiconductors Inc., 811 E. Arques Ave., Sunnyvale, CA 94088; (408) 991-2000; www.philips.com.

Cygnal Integrated Products Inc., 4301 Westbank Dr., Building B, Suite 100, Austin, TX 78746-6564; (512) 327-7088; www.cygnal.com.

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