[attachment=14713]
ECE 346 Microcontrollers
MC68HC11 Educational Board,
Input and Output
What is it?
Circuit board that has a 6811 microcontroller
Has additional peripheral devices to make it easy to evaluate the 6811 microcontroller
Serial interface, breadboard area, extra RAM, EEPROM
Can be configured in a variety of ways
Memory Map
The memory map is a way of diagramming memory usage
Note how different regions of memory are used
Shows how memory resources are allocated to different purposes.
6811 Memory Map
6811 – I/O ports
Ports A, B, C, D, E
Total 40 I/O Pins
To use ports, must do one of two things
Either put 6811 in single chip mode by jumpering MODA and unjumpering MODB
Design a circuit that emulates the port functions
6811 – I/O ports
Port A – 8-bits, 3 input only, 4 output only, 1 input or output
Port B – General purpose output register.
8-bits, write to port B register causes data to be latched and driven from the port pins
I/O Ports (Continued)‏
Port C - General Purpose, 8-bit bidirectional I/O port
Control individual bits to be input/output by setting respective bit in DDRC register to 0/1
Reset clears DDRC—PORTC is input immediately after reset
Port D – General Purpose, 6-bit bidirectional data port
Input/output mode controlled by DDRD register
6811 board uses lower two bits for serial I/O
Upper two bits are not used and are always 0
I/O Ports (Continued)‏
Port E – 8-bit fixed direction input port
Eight binary inputs, but your evaluation board reserves PE0 for a special function and is not available
Can also be used to support 8 analog input channels
Ports are Mapped to Memory
Text I/O
Buffalo subroutines—use in your programs
INCHAR  input ASCII character to AccA and echo back, loops until it gets something
OUTA  output AccA ASCII character to terminal
Print “A” on screen
OUTA EQU $FFB8 ;Buffalo OUTA
INCHAR EQU $FFCD ;Buffalo INCHAR
* Output a character
LDAA #$41
JSR OUTA
* Input a character
JSR INCHAR
Note the Buffalo subroutines that are called to output and input characters.