em78p468n ELAN Microelectronics Corp, em78p468n Datasheet - Page 47

• Manufacturer Part Number: em78p468n
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.6) 12.31.2007
(This specification is subject to change without further notice)
6.10 Infrared Remote Control Application/PWM Waveform
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
If the high-pulse width timer clock source is FT (this clock source can be set by IOCA1), then
If the low-pulse width timer clock source is FT (this clock source can be set by IOCA1);
Fm: main oscillator frequency
T
T
F
high
low
8 bit dow n c ounter
carrier
A uto-reload buf f er
Pre-s caler
pulse
Fs
Counter 2
pulse
(IOCC0)
(IOC91)
=
Generation
time
Fm
2
time
×
8
8
1 (
=
=
+
prescaler
prescaler
decimal
Pre-s caler
(IOC A 1)
Fcarrier
Fig. 6-20 IR/PWM System Block Diagram
HF
Fs: sub-oscillator frequency
×
of
×
1 ( +
1 ( +
T
C
(this clock source can be set by IOC91), then
RE register
ounter
decimal
decimal
High-Pulse Width Timer
8 bit dow n counter
A uto-reload buf f er
LGP
2
(IOCD0)
of
of
preset
F
H/W Modulator Circuit
IRE
T
low
8
8
8
high
value
pulse
F
F
pulse
T
T
(
width
IOCC
width
Low -Puls e Width Timer
8 bit dow n c ounter
A uto-reload buf f er
8-Bit Microcontroller
timer
( IOCE0)
0
))
timer
Pre-s caler
×
EM78P468N/L
(IOCA 1)
8
8
8
prescaler
value
value
(
IOCE
(
IOCD
IROUT pin
• 41
0
))
0
))