2.1)  The 68hc11 microcontroller 

    General

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    The 68hc11 is a powerful 8-bit data, 16-bit address microcontroller
    from Motorola with an instruction set that is similar to the older
    68xx (6801, 6805, 6809) parts.  Depending on the variety, the 68hc11
    has built-in EEPROM/OTPROM, RAM, digital I/O, timers, A/D converter,
    PWM generator, and synchronous and ansynchronous communications
    channels (RS232 and SPI).  Typical current draw is less than 10ma.


    Architecture

    CPU has two 8 bit accumulators (A & B) that can be concatenated to
    provide a 16 bit double accumulator (D).  Two 16 bit index registers
    are present (X,Y) to provide indexing to anywhere in the memory map.
    Having the two index registers means the 68hc11 is very good for
    processing data.  Although an eight bit processor, the 68hc11 has
    some 16 bit instructions (add, subtract, 16 * 16 divide, 8 * 8
    mulitply, shift, and rotates).  A 16 bit stack pointer is also
    present, and instructions are provided for stack manipulation.
    Typically mutliplexed address and data bus. Go back to previous website. 

			
    A-D Convertor - Typically 8 channel 8 bit A/D, although the G5 has a
    10 bit A/D.

    Serial Communications Interface (SCI) - Asynchronous serial
    communications; Data format - 1 Start, 8 or 9 data, and one stop bit.
    Data rate - 150 - 312500 Baud (312500 is using 4 mhz E clock)

    Serial Peripheral Interface (SPI) - Synchronous serial
    communications, comprises CLK, DATA IN, DATA OUT and optionally chip
    selects.  As well as using specific SPI devices, it is very easy to
    expand IO using the SPI and standard logic devices (e.g. 74HC595 and
    74HC165).


2.2)  68hc11 flavors

    The following are Motorola flavors:

    HC11 A Series
       8K ROM (A8), ROMless (A0,A1), 256 RAM, 512 EEPROM (A1,A8), SPI,
       SCI, 3 IC 5 OC, 8 channel 8 bit A/D

    HC11 C0
       Nice new device developed together with AT&T.  ROMless, on board
       bank switching to support memory maps of up to 256K.  Totally
       glueless interface - Chip selects on board, Read Enable and
       Write Enable signals now generated on chip.  256 RAM, 8 channel 8
       bit A/D - Good pricing

    HC11 D Series
       Smallest and lowest cost member of the hc11 Family.  ROMless (D0),
       4K ROM (D3), 4K EPROM (711D3) - No A-D or EEPROM.  Still has
       standard timers and serial ports