Maxim's high-speed microcontroller family includes a wide variety of 8051 microcontrollers which execute
instructions at a faster 4 clocks-per-machine-cycle rate compared to the 8051's original 12 clocks-per-machine
cycle speed. Some of the high-speed microcontrollers operate entirely from external program memory, such as
the DS80C310, while others contain internal EPROM or ROM program memory, such as the DS87C520/
DS83C520. All of these high-speed devices are pin-compatible with existing 8051 microcontrollers, so designs
can be upgraded in most cases simply by dropping in a faster device and making minor software adjustments.
In a similar manner, the ultra-high-speed flash microcontrollers can be used as drop-in upgrades for high-speed
microcontroller designs. These newer, more powerful microcontrollers, which include the DS89C430/DS89C450,
offer important improvements: expanded internal program flash memory (up to 64kB); and a redesigned, ultrahigh-
speed microcontroller core capable of executing instructions in a single clock cycle for up to a 12x speed
improvement over the original 8051 design.
This application note discusses how to upgrade from the high-speed microcontrollers to ultra-high-speed flash
devices. The article also outlines differences in feature sets, pinout details, and SFR changes that must be
considered when upgrading a design.