EM78P258N
8-Bit Microprocessor with OTP ROM
6.8 Infrared Remote Control Application/PWM Waveform
Generation
6.8.1 Overview
This LSI can easily output infrared carrier or PWM standard waveform. As illustrated
below, the IR and PWM waveform generation function include an 8-bit down count
timer/counter, high-time, low-time, and IR control register. The IROUT pin waveform is
determined by IOCA0 (IR and TCCC scale control register), IOCB1 (high-time rate,
low-time rate control register), IOC81 (TCCC counter), IOCA1 (high-time register), and
IOC91 (low-time register).
FT:CLK(Fosc)
8 Bit counter
8-to-1 MUX
8 Bit counter
8-to-1 MUX
8 Bit counter
8-to-1 MUX
Scale
(IOCB1)
Scale
(IOCB1)
Scale
(IOCA0)
8
8
Auto-reload buffer
(High-time)(IOCA1)
Auto-reload buffer
(Low-time)(IOC91)
8bit binary
down counter
8bit binary
down counter
8
8
Fcarrier
8bit binary
down counter
H/W Modulator
8
Auto-reload buffer
(TCCC)(IOC81)
HF
Underflow Interrupt
HPWTIF
LPWTIF
LG
IR
IROUT
Fig. 6-10 IR/PWM System Block Diagram
NOTE
Details of the Fcarrier high time width and low time width are explained below:
Fcarrier =
FT/ 2 { [1+decimal TCCC Counter value (IOC81)] * TCCC
Scale(IOCA0) }
High time width = { [1+decimal high-time value (IOCA1)] * High time Scale(IOCB1) } /
FT
Low time width = { [1+decimal low-time value (IOC91)] * Low time Scale(IOCB1) } /
FT
Where FT is the system clock FT=Fosc/1(CLK=2)
FT=Fosc/2(CLK=4)
Product Specification (V1.0) 06.16.2005
• 49
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
