M34551 View Datasheet(PDF) - Renesas Electronics

Part Name

Description

Manufacturer

M34551

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

Renesas Electronics 

MITSUBISHI MICROCOMPUTERS

4551 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for

INFRARED REMOTE CONTROL TRANSMITTER

Table 11 Carrier generating circuit control register and control flag

Carrier wave output control register C2

at reset : 02

at power down : 02

W

C20 Carrier wave output auto-control bit

0 Auto-control output by timer 1 is invalid

1 Auto-control output by timer 1 is valid

Carrier wave generating control flag CR

at reset : 02

at power down : 02

W

CR Carrier wave generating control

Note: “W” represents write enabled.

0 Carrier wave generating stop (SPCR instruction)

1 Carrier wave generating start (STCR instruction)

(1) Carrier generating circuit related registers

q Carrier wave selection register C1

Each carrier waveform can be selected by setting the register

C1. Set the contents of this register through register A with

the TC1A instruction.

q Carrier wave output control register C2

Timer 1 can auto-control the output enable interval and the

output disable interval of the carrier wave output from port

CARR by setting the register C2. Set the contents of this

register through register A with the TC2A instruction.

The setting of the output enable/disable interval is described

below.

ΠValidate the carrier wave output auto-control function

(C20=“1”).

 Select the carrier wave or the carrier wave divided by 2

as the timer 1 count source.

Ž Set the count value (the output enable interval of carrier

wave from port CARR) to timer 1.

 Operate timer 1 (W20=“1”).

 Operate the carrier generating circuit (STCR instruction

executed).

‘ Set the next count value (the output disable interval of

carrier wave from port CARR) to reload register R1 before

timer 1 underflow occurs.

The carrier wave is output from port CARR until the first timer

1 underflow occurs. The output of the carrier wave from port

CARR is disabled and the next count value is loaded from

reload register R1 to timer 1 by the first timer 1 underflow.

Then, the output of carrier wave is disabled until the second

timer 1 underflow. Also, the next enable interval of the carrier

wave output can be set by setting the third count value to

timer 1 reload register before the second timer 1 underflow

occurs. If the carrier wave output auto-control function is

invalidated (C20=“0”) while the carrier wave output is auto-

controlled, the output of port CARR retains the state when

the auto-control is invalidated regardless of timer 1 underflow.

This state can be terminated by timer 1 stop (W20=“0”). When

the carrier wave output auto-control function is validated

(C20=“1”) again after it is invalidated (C20=“0”), the auto-

control of carrier wave output is started again when the next

timer 1 underflow occurs.

(2) Carrier wave generating control flag (CR)

The CR flag is used to control the carrier wave generating

operation of the carrier generating circuit. The CR flag is “1”

and the carrier wave generating is started by executing the

STCR instruction. The CR flag is “0” and the carrier wave

generating is stopped by executing the SPCR instruction. The

CR flag is “0” at system reset.

(3) Note on the carrier generating circuit stop

In order to stop the carrier wave which has the cycle longer

than that of the instruction clock with the SPCR instruction,

stop it at the point when the carrier wave outputs “L” level in

the SPCR instruction execution cycle.

If this condition is not satisfied, the last “H” output interval of

carrier wave is shortened.

(4) Notes when using the carrier wave output auto-control function

q Execute the STCR instruction after setting the timer 1 and

register C2 in order to start the carrier generating circuit

operation.

q Stop the timer 1 (W20=“0”) after stopping the carrier

generating circuit (SPCR instruction executed) while the

carrier wave output is disabled in order to stop the carrier

wave output auto-control operation.

q If the carrier wave output auto-control function is invalidated

(C20=“0”) while the carrier wave output is auto-controlled,

the output of port CARR retains the state when the auto-

control is invalidated regardless of timer 1 underflow. This

state can be terminated by timer 1 stop (W20=“0”).

When the carrier wave output auto-control function is

validated (C20=“1”) again after it is invalidated (C20=“0”),

the auto-control of carrier wave output is started again when

the next timer 1 underflow occurs. However, when the carrier

wave output auto-control bit is changed during timer 1

underflow, the error-operation may occur.

q Use the carrier wave or the carrier wave divided by 2 as the

timer 1 count source when the carrier wave output auto-

control function is selected.

If the ORCLK is used as the count source, a hazard may

occur in port CARR output because ORCLK is not

synchronized with the carrier wave.

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