PD17225_15 Datasheet, PDF (37/86 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLER FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTER

µPD17225, 17226, 17227, 17228
Setting carrier frequency and duty factor
Where the system clock frequency is fX and carrier frequency is fC:
(division ratio) = fX/(2 × fC)
is divided into m:n and is set in the modulo registers as follows:
High-level period set value = { × m/(m + n)} – 1
Low-level period set value = { × n/(m + n)} – 1
Example Where fC = 38 kHz, duty factor (high-level period) = 1/3, and fX = 4 MHz,
= 4 MHz/(2 × 38 kHz) = 52.6
m:n = 1:2
From the above, the value of the modulo register is:
High-level period ^.=. 17
Low-level period ^.=. 34
Therefore, the carrier frequency is 37.74 kHz.
Table 5-1. Carrier Frequency List (fX = 4 MHz)
Set value
NRZHTMM
NRZLTMM
00H
00H
01H
02H
04H
04H
09H
09H
0FH
10H
0FH
21H
11H
21H
11H
22H
19H
35H
3FH
3FH
7FH
7FH
tH (µs)
0.5
1.0
2.5
5.0
8.0
8.0
9.0
9.0
13.0
32.0
64.0
tL (µs)
0.5
1.5
2.5
5.0
8.0
17.0
17.0
17.5
27.0
32.0
64.0
1/fC (µs)
fC (kHz)
1.0
2.5
5.0
10.0
16.5
25.0
26.0
26.5
40.0
64.0
120.0
1000
400
200
100
60.6
40.0
38.5
37.7
25.0
15.6
7.8
Duty
1/2
2/5
1/2
1/2
1/2
1/3
1/3
1/3
1/3
1/2
1/2
tH tL
REM
(fC)
1/fC
Data Sheet U12643EJ2V0DS00
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