New High Speed 8051-Compatible Microcontroller from Dallas Semiconductor

Dallas's new DS89C420 can operate up to 50MHz

Dallas Semiconductor (now part of Analog Devices) has released the DS89C420 Ultra High-Speed Microcontroller, the first completely 8051-compatible microcontroller to achieve peak processing speeds of one machine instruction per clock cycle, or 50 MIPS (million instructions per second) at a maximum clock speed of 50 MHz. This new benchmark represents a 50-fold performance gain over the original 8051 design and a six-fold gain over the next-fastest 8051 microcontrollers, which Dallas also pioneered.

Besides record-breaking speed, the DS89C420 features 16 kilobytes of Flash memory that allows programming in any of three modes: in-system, in-application or standard parallel programming. These enhancements result from a new redesign of the 8051 processing core and advanced memory address/access methods. At the same time, the DS89C420 remains 100% pin- and instruction-set compatible with existing 8051-based systems.

The familiar 8-bit 8051 architecture is widely used in control and interface functions for computer sub-systems and peripherals, household appliances, data and communications equipment, and industrial control and other commercial equipment. Using Dallas’s unique In-System Flash programming approach with the industry-standard pin-out, the DS89C420 can be assembled and shipped erased in the end equipment, then programmed on-site for application-specific purposes. Or it can simply replace an existing 8051-type microcontroller for significantly higher performance.

Frank Taylor, Dallas’ product manager for microcontrollers, said, “Aside from design compatibility, all microcontrollers remain subject to one major performance gauge: the speed at which they execute instructions. The need for faster processing led to Dallas' first redesign of the 8051, which reduced the number of clock cycles per machine instruction from 12 to 4.”

“We still wanted to break limits, however, so we overhauled the design again. The product of that effort, the DS89C420, is ultra high-speed and flexible. The maximum crystal speed has increased from 33 MHz to 50 MHz. Instead of 12 cycles or even 4, the DS89C420 uses one clock cycle to process many instructions, achieving 50 MIPS at peak performance.”

“This performance increase enables our 8051 design to more than meet the challenge from RISC (Reduced Instruction Set Computer) chips, which reduce the program instruction set to achieve speed. It potentially takes several RISC instructions to achieve the same result as one 8051 instruction. The DS89C420 has both superior speed and the power of the full 8051 instruction set.”

Flexible Memory Resources and Flash Programming
The DS89C420’s unique memory architecture contributes to faster processing and extends the concept of field programmability. Internal memory management logic enables application software to dynamically configure on-chip memory blocks by executing user software in one block while reprogramming the other. When that block is reprogrammed, software can switch the blocks so that the other can be erased and reprogrammed. The Flash boot loader supports in-system programming through the serial port, opening the entire Flash memory to an external program source. For a third programming mode, the DS89C420 also supports standard Flash or EPROM programmers.

In general, software written for existing 8051-based systems works with the DS89C420, with the exception of critical timing routines. Due to its innately greater speed, the DS89C420 provides a stretch cycle feature and page or non-page memory interface modes to enable communication with slower external memory and peripherals.

Additional Resources
The DS89C420 features two data pointers that can be used to move blocks of data both forwards and backwards. This unique capability to automatically increment or decrement the data pointer reduces the number of instruction steps and increases the speed of operation. Other resources include 13 interrupt sources with five priority levels instead of three, three 16-bit timer/counters and a watchdog timer. An internal clock divider circuit enables Power Management Mode, where the DS89C420 selects a processing speed based on software input and maintains all processes at lower power states without shutting down. Additionally, a clock multiplier is included to allow full-speed operation from lower speed, more readily available crystals.

The Analog Devices website address is www.analog.com
[Reprinted with kind permission from Dallas Semiconductor]