4559 datasheet(68/148 Pages) RENESAS

68 / 148 page

Rev.1.04

Aug 23, 2007

Page 68 of 146

REJ03B0188-0104

4559 Group

LIST OF PRECAUTIONS

(1) 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.

CNVSS is also used as VPP pin. Accordingly, when using this pin,

connect this pin to VSS through a resistor about 5k

Ω (connect

this resistor to CNVSS/VPP pin as close as possible).

(2) Note on Power Source Voltage

When the power source voltage value of a microcomputer is less

than the value which is indicated as the recommended operating

conditions, the microcomputer does not operate normally and

may perform unstable operation.

In a system where the power source voltage drops slowly when

the power source voltage drops or the power supply is turned off,

reset a microcomputer when the supply voltage is less than the

recommended operating conditions and design a system not to

cause errors to the system by this unstable operation.

(3) Register initial values 1

The initial value of the following registers are undefined after

system 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)

(4) 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)

(5) Program counter

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

built-in ROM.

(6) Stack registers (SKS)

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

subroutines 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.

Accordingly, be careful not to over the stack when performing

these operations together.

(7) Multifunction

• The input/output of D5 can be used even when INT is used. Be

careful when using inputs of both INT and D5 since the input

threshold value of INT pin is different from that of port D5.

• “H“ output function of port C can be used even when the

CNTR (output) is used.

(8) Power-on reset

When the built-in power-on reset circuit is used, set the time for

the supply voltage to rise from 0 V to the minimum voltage of

recommended operating conditions to 100

µs or less.

If the rising time exceeds 100

µs, connect a capacitor between

the RESET pin and Vss at the shortest distance, and input “L”

level to RESET pin until the value of supply voltage reaches the

minimum operating voltage.

(9) POF, POF2 instruction

When the POF or POF2 instruction is executed continuously

after the EPOF instruction, system enters the RAM back-up

state.

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

executing only the POF or POF2 instruction.

Be sure to disable interrupts by executing the DI instruction

before executing the EPOF instruction and the POF/POF2

instruction continuously.

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