4280 datasheet(15/48 Pages) RENESAS

15 / 48 page

MITSUBISHI MICROCOMPUTERS

4280 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTERS

CARRIER GENERATING CIRCUIT

The 4280 Group can output the various carrier waveforms by

the carrier wave selection register C.

Set the contents of this register through register A with the TCA

instruction. The TAC instruction can be used to transfer the

contents of register C to register A. When the TCA instruction is

executed, the output latch of port CARR is cleared to “0.”

The carrier waveform selected by setting register C can be output

from port CARR by setting port CARR output latch to “1.” When

the CARR output latch is cleared to “0,” carrier wave output is

stopped and port CARR output is fixed to “L” level. The CARR

output latch can be set through bit 3 (A3) of register A with the

OCRA instruction.

The relationship between the setting value of register C and

selected waveform is described below.

Also, timer 1 can auto-control the carrier wave output from port

CARR by setting the timer control register V1.

Fig. 15 Carrier wave selection register

No carrier wave

1/4

1/2

1/3

1/2

O CRA

(TC A)

f(XIN)/4

1/2

(Note)

Carrier wave selection register C (at reset: 1112, at RAM back-up: 1112)

setting value

C1 C0

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

“H”

“L”

Output waveform

Carrier wave

Frequency

Duty

System clock/

System clock

“L” level fixed

Note: This carrier wave can be used only when system clock f(XIN)/8 is selected.

The carrier wave output is fixed to “L” level when system clock f(XIN) is selected.

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