The 68HC11 microcontroller is a computer chip originally introduced by Motorola in 1985. It is called a microcontroller rather than a microprocessor because it is designed for a specific use as an embedded application, rather than a general purpose processor in a personal computer, smartphone or other device. The 68HC11 is now produced and distributed by Freescale Semiconductor. Microcontrollers
. are automatically controlled devices that control items such as implantable medical devices, automobile engine controls, appliances, tools and the like. They have a limited number of functions built in which are not changeable. They include a processor core, memory and output peripherals on one single chip, compared to a general purpose unit that has these functions on separate components. The great advantage of microcontrollers like the 68HC11 is their ability to run for long periods of time in a wait mode, drawing very little power (on the order of nanowatts) while awaiting a button press or other input. This makes them ideal for long-lasting battery applications, although they can also be used in higher power modes, with faster clock speeds and correspondingly higher power consumption. Programming a 68HC11 requires knowledge of low-level assembler type languages. Old computers running DOS are perfectly suitable for this use, and there are many utility programs available on the Internet designed for this purpose. Once the program is written, it is compiled into 68HC11 machine code and injected into the chip using an EEPROM, or electrically erasable programmable read only memory, which is the memory on the 68HC11 itself. The processor on the chip then reads the EEPROM and executes the program. The ready availability of these programming tools makes this chip an excellent choice for the hobbyist, particularly those working in amateur robotics. The programs can be easily rewritten and re-inserted into the microcontroller, making changes and modifications of programming relatively simple. http://www.technologicalarts.com/myfiles/apps.html or http://home.earthlink.net/~tdickens/68hc11/basics.html
