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6.10 Infrared Remote Control Application/PWM Waveform Generate
This LSI can output infrared carrier in user-friendly or in PWM standard waveform. The IR
and PWM waveform generated functions include an 8-bit down count timer/counter,
high-pulse width timer, low-pulse width timer, and IR control register. The IR system block
diagram is shown in Fig. 6-20. The IROUT pin waveform is determined by IR control
register (RE), IOC90 (Counters 1 and 2 control register), IOCA0 (high-pulse width timer,
low-pulse width timer control register), IOCC0 (Counter 2 preset), IOCD0 (high-pulse width
timer preset register), and IOCE0 (low-pulse width timer preset register). Details on
Fcarrier, high-pulse time, and low pulse time are explained as follows :
If Counter 2 clock source is F
F
carrier
If the high-pulse width timer clock source is FT (this clock source can be set by IOCA1), then
T
high
pulse
If the low-pulse width timer clock source is FT (this clock source can be set by IOCA1);
T
low
pulse
Fs
Pre-s caler
(IOC91)
8 bit dow n c ounter
A uto-reload buf f er
Counter 2
(IOCC0)
Fm: main oscillator frequency Fs: sub-oscillator frequency
Product Specification (V1.5) 02.15.2007
(This specification is subject to change without further notice)
(this clock source can be set by IOC91), then
T
=
×
+
2
1 (
decimal
of
×
1 ( +
prescaler
=
time
×
1 ( +
prescaler
=
time
Fm
Pre-scaler
(IOC A 1)
Fcarrier
8
HF
8
Fig. 6-20 IR/PWM System Block Diagram
EM78P468N/EM78P468L
F
T
C
ounter
2
preset
value
decimal
of
high
F
decimal
of
low
pulse
F
High-Pulse Width Timer
(IOCD0)
8
A uto-reload buf f er
8
8 bit dow n counter
8
H/W Modulator Circuit
LGP
IRE
RE register
8-Bit Microcontroller
×
(
IOCC
0
))
prescaler
pulse
width
timer
value
T
width
timer
value
T
Pre-s caler
(IOCA 1)
Low -Puls e Width Timer
( IOCE0)
8
A uto-reload buf f er
8
8 bit dow n counter
8
(
IOCD
0
))
(
IOCE
0
))
IROUT pin
• 41
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