EM78P468L Datasheet, PDF (51/83 Pages) ELAN Microelectronics Corp – 8-BIT Microcontroller

EM78P468L
8-BIT Microcontroller
4.10 Infrared Remote Control Application / PWM Waveform
Generate
This LSI can output infrared carrier in a friendly manner 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 show in Fig.21, The IROUT pin waveform is determined by IR
control register (RE), IOC90 (Counter 1, 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 source clock is F_T (this clock source can set by IOC91);
F_carrier = _{2 * (1+ decimal}
of
F_T
counter2 preset value(IOCC0)) * prescaler
If high-pulse width timer source clock is FT (this clock source can set by IOCA1);
prescaler * (1+ decimal of high pulse width timer value(IOCD0))
T_{high pulse time} =
F_T
If low-pulse width timer source clock is FT (this clock source can set by IOCA1);
prescaler * (1+ decimal of low pulse width timer value(IOCE0))
T_{low pulse time} =
F_T
Pre-s caler
(IOCA 1)
Fs Fm
Pre-s caler
(IOC91)
Pre-s caler
(IOC A 1)
Fcarrier
High-Pulse Width Timer
(IOCD0)
8
A uto-reloadbuf f er
8
8 bit dow n counter
8
Low -Puls e Width Timer
( IOCE0)
8
A uto-reloadbuf f er
8
8 bit dow n c ounter
8
8 bit dow n c ounter
H/W Modulator Circuit
8
A uto-reloadbuf f er
HF
LGP
IRE
8
Counter 2
(IOCC0)
REregister
Fm: main oscillator frequency; Fs: sub-oscillator frequency
Fig. 21 IR/PWM System Block Diagram
IR O U Tp in
Product Specification (V1.0) 03.15.2006
(This specification is subject to change without further notice)
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