Electrical Engineering Technology
SUNY College of Technology, Alfred, NY
ELET 2143 Embedded Controller Fundamentals
Fall Semester 2007
PRELAB 6. Generating Musical Notes with the 68HC11
NAME:________________________________
PRELAB
Hand in your Prelab at the beginning of your lab section, otherwise, you will lose 25% of your grade in this lab.
In this lab you will be asked to write a program in assembly language for the 68HC11 microcontroller that will generate the
musical notes given in Table II. You will be given a speaker to connect to pin 6 of Port A. The address of Port A is at $1000.
Question 1: Research about the Port A in the 68HC11. Look at the internet or microcontroller books about the Port A (the
Motorola manual is a good resource). Indicate which bits are inputs, which ones are outputs, and which ones are bidirectional
(input/output). Give your answer in the following table:
Port A
Input ?
Output ?
Input/Output ?
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
Question 2: Look at the Adapt 11 manual and fill out the following table
Port A
Pin # in connector H1
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
Question 3: Study the assembly code given in Table I, and modify it adequately to write a program that can play the 10
musical notes given in Table II. Adjust your counter and delays in such a way that the musical scale is agreeable to the
human ear. For example, in order to generate the note E ( f = 330 Hz) your program has to send the following periodic signal
to the speaker (pin PA6)
f = 330 Hz, T = 1/f = 1/330 = 3.03 ms,
then : t1 = t2 = 1.515 msec.
The delay routine has to generate this 1.515 ms.
The values given in the Delay routine in Table I
generate this particular frequency.
AGAIN:
t1
LOOP1:
ORG
LDAB
LDAA
STAA
JSR
LDAA
STAA
JSR
DECB
BNE
SWI
; This is a
LDY
DEY
BNE
RTS
$2000
#$70
#%00000000
$1000
t1
#%01000000
$1000
t1
AGAIN
Subroutine
#$0BD7
; register B will count the number of periods in the square wave
; write a zero to PA6
; jump to the delay subroutine
; write a “1“ to PA6
; jump to the delay subroutine
; decrement the counter
; have the number periods in the square wave been completed ?
; stop
that generates an approximated 1.5 msec delay
; Delay routine
; approx. time 1.5 msec
LOOP1
; return from the subroutine
TABLE I. Assembly code that generates the musical note E
low
middle
high
no
NOTE
B
C
D
E
F
G
A
B
C
D
sound
FREQUENCY
247 Hz
262 Hz
294 Hz
330 Hz
349 Hz
392 Hz
440 Hz
494 Hz
523 Hz
587 Hz
0 Hz
TABLE II. Frequencies of musical notes
Frequencies of more notes:
http://www.phy.mtu.edu/~suits/notefreqs.html