4518 Datasheet, PDF (71/160 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4518 Group
LIST OF PRECAUTIONS
➀Noise 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 kΩ (connect this resistor to CNVSS/
VPP pin as close as possible).
➁Register 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)
➂Register 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)
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.
➇Reading 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.
➈Writing 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.
10 _{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.
11 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.
Rev.3.01 2005.06.15 page 71 of 157
REJ03B0008-0301