2003 University of Illinois at Chicago ECE 367 V. Goncharoff
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ECE 367 - Microprocessor-Based Design
Homework #4: Due in lab during the fourth lab meeting (Week 6)
Design a 68HC11 assembly language program that implements a 3-digit free-
running decimal timer, with 0.1 sec resolution, using the circuit below (seven-
segment LED displays are of the common cathode type). Do not use interrupts.
The 7-segment displays must be driven in multiplexed mode. Count "00.0" should
follow "99.9" sec. The counter should keep exact time (assuming E = 2 MHz
clock). Provide printed code listing; comment every line; include software
flowchart.
MC68HC11
microcontroller
a
b
c
d
f
e
g
sec x 1sec x 10 sec x 0.1
Cathode 1 Cathode 2 Cathode 3
Gnd
7 7 7
PB0 - PB6 PC0 - PC6 PD0 - PD5, PA4
21
For example: a = PB0, b = PB1, c = PB2, d = PB3, e = PB4, f = PB5, g = PB6.
Output
Ports
