MITSUBISHI MICROCOMPUTERS
4280 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTERS
CARRIER GENERATING CIRCUIT
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.
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.
Carrier wave selection register C (at reset: 111
2, at RAM back-up: 111
2)
Register C
setting value
Output waveform
Carrier wave
(TCA)
LA
8
O CRA
O CRA
LA
0
Frequency
Duty
C2
C1
C0
0
0
0
1
1
0
0
1
1
0
“H”
“L”
1/3
1/2
System clock/
12
0
0
0
1
1
1
1
1
0
1
0
1
0
1
“H”
“L”
“H”
“L”
1/4
1/2
1/2
System clock/
8
“H”
“L”
“H”
“L”
System clock
“H”
“L”
No carrier wave
f(XIN)/4
(Note)
1/2
“H”
“L”
“H”
“L”
“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.
Fig. 15 Carrier wave selection register
MITSUBISHI
ELECTRIC
14
MITSUBISHI [ Mitsubishi Group ]
