IBM MiEM78P468N, MiEM78P468L manual Infrared Remote Control Application/PWM Waveform Generate

EM78P468N/EM78P468L

8-Bit Microcontroller

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 FT (this clock source can be set by IOC91), then

Fcarrier =					FT
	2 ⋅ (1 + decimal		of C ounter	2	preset	value	( IOCC 0)) ⋅ prescaler
If the high-pulse width timer clock source is FT (this clock source can be set by IOCA1), then
		prescaler	⋅ (1 + decimal	of	high	pulse	width timer value ( IOCD 0))
Thigh pulse time =
						FT

If the low-pulse width timer clock source is FT (this clock source can be set by IOCA1);

Tlow pulse time

Fs Fm

prescaler	⋅ (1 + decimal	of	low	pulse	width	timer value	( IOCE 0))
=				FT
						Pre-scaler
						(IOCA1)
	High-Pulse Width Timer			Low -Pulse Width Timer
		(IOCD0)			( IOCE0)
		8				8
	A uto-reloadbuffer				A uto-reloadbuffer

Pre-scaler

(IOC A1)

Pre-s caler

(IOC91)

Fcarrier

8 bit dow n counter

8

		8		8
8 bit dow n counter			8 bit dow n counter
	8			8

H/W Modulator Circuit

IROUTpin

A uto-reloadbuffer HF LGP IRE

8

Counter 2 (IOCC0)

REregister

Fm: main oscillator frequency Fs: sub-oscillator frequency

Fig. 6-20 IR/PWM System Block Diagram

Product Specification (V1.5) 02.15.2007 • 41

(This specification is subject to change without further notice)