Memory Address	   Function
		==============  ================
		|	$0000	
		|	$00FF	   RAM Memory
		|	$0100
		|	$0FFF	   unused
		|	$1000
		|	$103F	   Special Registers
		|	$1040
		|	$F7FF	   unused
		|	$F800
		|	$FFFF	   EEPROM Memory
		=================================
	Memory Map of the MC68HC11E2 Microprocessor
The memory map is a table of all the memory a 68HC11E2 is able to address and what function that particular area of memory serves. No external memory is used on the Miniboard, that is, only on chip memory is used. The internal memory map of a 6811 chip is 64K bytes large, but very little of this area is actually usable. Memory locations are addressed by a 4 digit hexadecimal number ranging from $0000 to $FFFF. Each hexadecimal address corresponds to one byte (8 bits) of memory. Different areas of the memory serve different functions and may be dedicated to RAM, special registers, or EEPROM.

RAM is used to store variables and stack information during program execution, there is 256 bytes of RAM in the memory map starting at $0000 and extending to $00FF. RAM is volatile memory and will be lost every time there is a power interruption to the microcontroller.

Special registers are used by the Miniboard to configure and or effect various systems on the board like ports, timers, interrupts, and the A to D system. Much of a 6811 programmers task involves reading and writing values from/to these registers. The special registers exit in the memory map from $1000 to $103F.

EEPROM is the area of memory where the program is stored. This area is 2K bytes and therefore, Miniboard programs may only be 2K bytes in size (not including space dedicated to variables and constants which live in RAM). EEPROM is located in the memory map from $F800 to $FFFF. So the Miniboard programmer must ensure that the first byte of his/her program loads into memory at $F800 and that the reset vector will point to $F800. EEPROM is non-volatile, that is, it will be retained in state during power interruptions regardless of how long the power stays off (however, heavy current drains, as from a stalled motor, could cause EEPROM memory corruption). EEPROM may be written to during program execution, but this is very costly both in terms of time and power consumed from a battery so it is very seldom done. Most programmers will find that they download a program into EEPROM and never write to it again thinking of this memory area as if it were ROM after the download.

ieeecs@hal.elee.calpoly.edu
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