4570 datasheet(36/69 Pages) RENESAS

36 / 69 page

MITSUBISHI MICROCOMPUTERS

4570 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

LIST OF PRECAUTIONS

Noise and latch-up prevention

Connect a capacitor on the following condition to prevent noise

and latch-up;

• connect a capacitor (approx. 0.1

µF) between pins VDD and

VSS at the shortest distance,

• equalize its wiring in width and length, and

• use the thickest wire.

In the One Time PROM version, CNVSS pin is also used as

VPP pin. Accordingly, when using this pin, connect this pin to

VSS through a resistor about 5 k

Ω (connect this resistor to

CNVSS/VPP pin as close as possible).

Prescaler

Stop the prescaler operation to change its frequency dividing

ratio.

Count source

Stop timer 1, timer 2 or timer 3 counting to change its count

source.

Reading the timer count value

Stop each of the timers and then execute the TAB1, TAB2 or

TAB3 instruction to read timer 1, 2 or 3 data.

Writing to reload register R1

When writing the data to reload register R1 while timer 1 is

operating, avoid a timing when timer 1 underflows.

Writing to reload register R3H

When writing the data to reload register R3H while timer 3 is

operating, avoid a timing when timer 3 underflows.

Notes on timer 3 operation start

Set the timer 1 and register C2 before timer 3 is started to

operate (W33=“1”).

Notes on carrier wave output auto-control operation stop

Stop the timer 1 (W10=“0”) after stopping the timer 3 (W33=“0”)

while the carrier wave output is disabled in order to stop the

carrier wave output auto-control operation.

Notes on setting carrier wave output control regiter C2

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.

When the carrier wave output auto-control function is validated

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

by timer 1 is validated again when the next timer 1 underflow

occurs.

However, when the carrier wave output auto-control bit (C20)

is changed during timer 1 underflow, the error-operation may

occur.

Notes on timer 1 count source

When the carrier wave output auto-control function is selected,

use the carrier wave CARRY as the timer 1 count source.

If the ORCLK is used as the count source, a short pulse may

occur in port CARR output because ORCLK is not

synchronized with the carrier wave.

Notes on writing to reload register R1 when carrier wave output

auto-control operation

When the carrier wave output auto-control function is selected

and data is set to reload register R1 while timer 1 is operating,

avoid the timing that the contents of timer 1 becomes “0” to

execute the T1AB instruction.

One Time PROM version

The operating power voltage of the One Time PROM version

is within the range of 2.5 V to 5.5 V.

Multifunction

Note that the port D9 output function and P21 input function

can be used even when TOUT and INT pin function is selected.

POF instruction

Note that system cannot enter the RAM back-up state when

executing only the POF instruction.

Execute the POF instruction immediately after executing the

EPOF instruction to enter the RAM back-up.

Be sure to disable interrupts by executing the DI instruction

before executing the EPOF instruction.

Program counter

Make sure that the PCH does not specify after the last page of

the built-in ROM.

P21/INT pin

When the interrupt valid waveform of P21/INT pin is changed

with the bit 2 of register I1 in software, be careful about the

following notes.

• Clear the bit 0 of register V1 to “0” and then change the

interrupt valid waveform of P21/INT pin with the bit 2 of

• Clear the bit 2 of register I1 to “0” and execute the SNZ0

instruction to clear the EXF0 flag after executing at least

one instruction (refer to Figure 34). Depending on the input

state of the P21/INT pin, the external 0 interrupt request flag

(EXF0) may be set to “1” when the interrupt valid waveform

is changed.

; (!!!02)

TV1A

; The SNZ0 instruction is valid

TI1A

; Change of the interrupt valid waveform

NOP

SNZ0

;The SNZ0 instruction is executed

NOP

...

! : this bit is not related to the setting of INT.

Fig. 34 External 0 interrupt program example

4570 Datasheet(PDF) 36 Page - Renesas Technology Corp

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