4501 datasheet(52/116 Pages) RENESAS

52 / 116 page

Rev.3.01

2005.02.07

page 52 of 112

REJ03B0104-0301

4501 Group

Electric Characteristic Differences Between Mask ROM and One

Time PROM Version MCU

There are differences in electric characteristics, operation margin,

noise immunity, and noise radiation between Mask ROM and One

Time PROM version MCUs due to the difference in the manufac-

turing processes.

When manufacturing an application system with the One time

PROM version and then switching to use of the Mask ROM ver-

sion, please perform sufficient evaluations for the commercial

samples of the Mask ROM version.

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.

Power-on reset

Reset can be automatically performed at power on (power-on re-

set) by the built-in power-on reset circuit. When the built-in

power-on reset circuit is used, the time for the supply voltage to

rise from 0 V to 2.0 V must be set 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 RE-

SET pin until the value of supply voltage reaches the minimum

operating voltage.

Clock control

Execute the CMCK or the CRCK instruction in the initial setting

routine of program (executing it in addres 0 in page 0 is recom-

mended).

The oscillation circuit by the CMCK or CRCK instruction can be

selected only at once. The oscillation circuit corresponding to the

first executed one of these two instruction is valid. Other oscilla-

tion circuits and the on-chip oscillator stop.

On-chip oscillator

The clock frequency of the on-chip oscillator depends on the sup-

ply voltage and the operation temperature range.

Be careful that variable frequencies when designing application

products.

Also, the oscillation stabilize wait time after system is released

from reset is generated by the on-chip oscillator clock. When

considering the oscillation stabilize wait time after system is re-

leased from reset, be careful that the variable frequency of the

on-chip oscillator clock.

External clock

When the external signal clock is used as the source oscillation

(f(XIN)), note that the RAM back-up mode (POF and POF2 in-

structions) cannot be used.

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