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NEC PD754144 User Manual

Page 168

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CHAPTER 6 PERIPHERAL HARDWARE FUNCTION

168

User’s Manual U10676EJ3V0UM

(3) Application of CG mode

To use the timer counter as a carrier generator for remote controller signal transmission

The examples shown below apply to the operation of the

µPD754244 at f

X

= 4.19 MHz. With f

X

= 6.0 MHz

operation of the

µPD754244 and f

CC

= 1.0 MHz operation of the

µPD754144, the cycles and signal output

periods are different even if the settings are the same.

<1> To generate a carrier clock with a frequency of 38.0 kHz (cycle of 26.3

µs) and a duty factor of 1/3

Set the higher 4 bits of the timer counter mode register (TM2) to 0011B and select 61.0

µs as the

longest set time.

Set the lower 4 bits of TM2 to 1111B, and select the CG mode and count operation. Then, issue

the timer start command.

Set the timer counter output enable flag (TOE2) to “1” to enable timer output.

Set the high-level period setting timer counter modulo register (TMOD2H) as follows.

– 1 = 36.8 – 1

36 = 24H

The set value of the timer counter modulo register (TMOD2) is as follows.

– 1 = 73.7 – 1

73 = 49H

SEL

MB15

;

or CLR1 MBE

MOV

XA, #024H

MOV

TMOD2H, XA

;

Sets modulo (high-level period)

MOV

XA, #49H

MOV

TMOD2, XA

;

Sets modulo (low-level period)

MOV

XA, #00111111B

MOV

TM2, XA

;

Sets mode and starts timer

1

26.3

µs

3

238 ns

2

26.3

µs

3

238 ns

.

.

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