4518 datasheet(71/160 Pages) RENESAS

71 / 160 page

Rev.3.01

2005.06.15

page 71 of 157

REJ03B0008-0301

4518 Group

➃ Stack registers (SKS)

Stack registers (SKs) are eight identical registers, so that subrou-

tines can be nested up to 8 levels. However, one of stack

registers is used respectively when using an interrupt service

routine and when executing a table reference instruction. Accord-

ingly, be careful not to over the stack when performing these

operations together.

➄ Multifunction

• The input/output of P30 and P31 can be used even when INT0

and INT1 are selected.

• The input of ports P20–P22 can be used even when SIN, SOUT

and SCK are selected.

• The input/output of D6 can be used even when CNTR0 (input) is

selected.

• The input of D6 can be used even when CNTR0 (output) is selected.

• The input/output of D7 can be used even when CNTR1 (input) is

selected.

• The input of D7 can be used even when CNTR1 (output) is selected.

➅ Prescaler

Stop counting and then execute the TABPS instruction to read

from prescaler data.

Stop counting and then execute the TPSAB instruction to set

prescaler data.

➆ Timer count source

Stop timer 1, 2, 3 and 4 counting to change its count source.

➇ Reading the count value

Stop timer 1, 2, 3 or 4 counting and then execute the data read

instruction (TAB1, TAB2, TAB3, TAB4) to read its data.

➈ Writing to the timer

Stop timer 1, 2, 3 or 4 counting and then execute the data write

instruction (T1AB, T2AB, T3AB, T4AB) to write its data.

Writing to reload register R1, R3, R4H

When writing data to reload register R1, reload register R3 or re-

load register R4H while timer 1, timer 3 or timer 4 is operating,

avoid a timing when timer 1, timer 3 or timer 4 underflows.

Timer 4

Avoid a timing when timer 4 underflows to stop timer 4 at the use

of PWM output function.

When “H” interval extension function of the PWM signal is set to

be “valid”, set “1” or more to reload register R4H.

LIST OF PRECAUTIONS

➀ Noise and latch-up prevention

Connect a capacitor on the following condition to prevent noise

and latch-up;

• connect a bypass capacitor (approx. 0.1

µF) between pins VDD

and VSS at the shortest distance,

• equalize its wiring in width and length, and

• use relatively thick 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).

➁ Register initial values 1

The initial value of the following registers are undefined after sys-

tem is released from reset. After system is released from reset,

set initial values.

• Register Z (2 bits)

• Register D (3 bits)

• Register E (8 bits)

➂ Register initial values 2

The initial value of the following registers are undefined at RAM back-

up. After system is returned from RAM back-up, set initial values.

• Register Z (2 bits)

• Register X (4 bits)

• Register Y (4 bits)

• Register D (3 bits)

• Register E (8 bits)

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