
W741L250
Publication Release Date: March 1998
- 11 -
Revision A2
If the Timer 1 clock input is F
T, then
:
Desired Timer 1 interval = (preset value +1) / F
T
Desired frequency for MFP output pin = F
T
÷
(preset value + 1)
÷
2 (Hz)
Preset value: Decimal number of Timer 1 preset value, and
F
OSC
: Clock oscillation frequency
Auto-reload buffer
8 bits
MR1.1
External clock
via RC.0
1. MR1.3 = 1
2. MOV TM1, #I
Underflow
signal
EVF.7
MFP
MFP signal
MR1.2
output pin
8-bit Binary
Down Counter
(Timer 1)
2
circuit
Reset
Reset
Disable
Enable
Fosc/64
Fosc
MR1.0
S
R
Q
1. Reset
2. INT 7 accept
3. CLR EVF, #80H
4. Set MR1.3 to 1
5. MOV TM1, #I
T
F
1. MR1.3 = 0
4
4
MOV TM1H, R
MOV TM1L, R
Set MR1.3 to 1
MOV TM1, #I
8
MOV TM1, #I
Figure 6. Organization of Timer 1
For example, when F
T
equals 32768 Hz, depending on the preset value of TM1, the MFP pin will
output a single tone signal in the tone frequency range from 64 Hz to 16384 Hz. The relation between
the tone frequency and the preset value of TM1 is shown in the table below.
3
4
5
Tone
frequency
130.81
138.59
146.83
155.56
164.81
174.61
185.00
196.00
207.65
220.00
233.08
246.94
TM1 preset value &
MFP frequency
7CH
75H
6FH
68H
62H
5DH
58H
53H
4EH
49H
45H
41H
Tone
frequency
261.63
277.18
293.66
311.13
329.63
349.23
369.99
392.00
415.30
440.00
466.16
493.88
TM1 preset value &
MFP frequency
3EH
3AH
37H
34H
31H
2EH
2BH
29H
26H
24H
22H
20H
Tone
frequency
523.25
554.37
587.33
622.25
659.26
698.46
739.99
783.99
830.61
880.00
932.23
987.77
TM1 preset value &
MFP frequency
1EH
1CH
1BH
19H
18H
16H
15H
14H
13H
12H
11H
10H
C
C#
D
D#
E
F
F#
G
G#
A
A#
B
131.07
138.84
146.28
156.03
165.49
174.30
184.09
195.04
207.39
221.40
234.05
248.24
260.06
277.69
292.57
309.13
327.68
372.36
390.09
420.10
443.81
442.81
468.11
496.48
528.51
564.96
585.14
630.15
655.36
712.34
744.72
780.19
819.20
862.84
910.22
963.76
T
O
N
E
Note: Central tone is A4 (440 Hz).