The 8031 Microcontroller Family ------------------------------------------------------------------------------- The original 8031 was developed by Intel. With the exception of microcontrollers that have sacrificed features to reduce the pin count (including, in some cases, reduced on-chip RAM), all members of the family have at least the 8031's capabilities. These include: * 128 Bytes of Internal RAM: This RAM is easily accessible through a rich instruction set. * Four 8-bit ports: These ports provide 32 bits of bidirectional I/O. In the romless versions (such as the 8031) or when external RAM was required, 18 of these pins became the address, data, and control busses. The 8 low-order address bits are multiplexed with the 8 data bits. * Up to 64Kbytes of off-chip ROM and RAM: All 8031 series processors have separate code and data space. Instructions are available to read data from code space. Because the 8031 only has a single 16-bit data pointer, access to external data is slower than access to internal RAM. External code runs at full speed. * 111 Instructions: 64 of these execute in a single cycle. At 12Mhz the 8031 reaches a peak execution speed of 1 MIPS. * Few External Parts Required: Minimum possible system is an 8031, 1 crystal, three capacitors, one resistor, a 74373 address latch and one EPROM. In this configuration, 14 bidirectional port pins are left for user use. * High Integration: On-chip resources include timers and counters, a two-level interrupt structure, and a bidirectional serial port. The 8032 doubled the amount of on-chip RAM to 256 bytes and added a third counter/timer. The 8751H added 4K bytes of on-chip EPROM which can be secured to protect proprietary code. Another advantage of on-chip EPROM is that it frees all of the port pins for user use when external RAM is not required. The 8xC51 series added several reduced power consumption options. The 8051 added 4K of on-chip mask ROM. This chip is of little interest to hobbyists because it cannot be ordered in small quantities. If you find one of these, you can tie the EA pin low and it will act like an 8031. All of the aforemention parts are available from Intel, Philips and AMD. ------------------------------------------------------------------------------- Interesting 8031 derivatives from various manufacturers include: * Dallas Semiconductor DS5000T: This amazing module integrates a specialized 80C32 core, 8 or 32 Kbytes of battery-backed RAM partitionable between code and data, serial port programmability, a real-time clock, a watchdog timer, a power-fail warning interrupt, on-chip reset generation, enhanced software security, and up to 16Mhz execution. This is a hacker's dream component. * Dallas Semiconductor DS80C320: An 8032 compatible that executes code three times faster at the same clock speed. Includes numerous other enhancements. * Dallas Semiconductor DS87C520: This processor executes 8031 code at a speed comparable to an 8031 running at 82.5Mhz! It includes 16Kbytes of securable EPROM, 1Kbyte of extra on-chip ram (above the 256 bytes standard for 8032 compatibles), an extra 16-bit pointer, a second serial port, dramatically enhanced power management, extra external interrupts, and too many other features to list here. * Dallas Semiconductor DS87C530: Similar to the above processor with the addition of an included real-time clock. * Philips 87C750: An 8031 derivative with 1K EPROM, 64 bytes of RAM, packaged in a 24-pin skinny DIP. Low cost and small. * Philips 80C562: 8K EPROM, 256 bytes RAM, 6 8-pin ports, 8 channel 8-bit ADC and various other features. * Intel 87C51GB: Features an extended temperature range (-40 to 125 degrees C), 8 Kbytes EPROM, two counter arrays with high-speed I/O, capture/compare, pulse width modulate, and watchdog timer modes, 8-bit 8-channel analog-to-digital conversion, enhanced serial port, schmitt trigger inputs, extra external interrupts, and more. This device is especially suited for automotive applications. * Intel 87C51FC: Features low power consumption, 32 Kbytes of on-chip EPROM, one counter array as above and one less-sophisticated counter, and an enhanced serial port. * Intel 80C152JC: This device features an 8031 core with a massively enhanced serial port (2.048 Mbaud capability, SDLC/HDLC, and CSMA/CD), DMA channels, HOLD and HOLDA, sophisticated power management, and more. For increased throughput, the serial port feeds a 3-byte FIFO. A CRC generator is provided in hardware. This part can, if you want it to, automatically conduct a move between two locations in external RAM or between external RAM and an SFR in the backgound as your code continues to execute (at reduced speed)! You can also program it to automatically store data received by the serial port at incrementing RAM locations or automatically send data out the serial port from incrementing RAM locations! This capability is available for both the enhanced serial port and the regular 8031-style serial port (simultaneously if you want). Many more derivatives are available. Write to Intel, Dallas Semiconductor, Philips, and Advanced Micro Devices for more information. Note: Every attempt has been made to be as complete, accurate, and up-to-date as possible. Nevertheless, always check with the manufacturer to ensure that you have the latest and most accurate information possible. The above descriptions are rough summaries intended to help you know where to look. There is no substitute for proper reseach and a thorough understanding of the manufacturer's specifications.