4518 datasheet(77/160 Pages) RENESAS

77 / 160 page

Rev.3.01

2005.06.15

page 77 of 157

REJ03B0008-0301

4518 Group

External clock

When the external clock signal for the main clock (f(XIN)) is used,

connect the clock source to XIN pin and XOUT pin open. In pro-

gram, after the CMCK instruction is executed, set main clock

(f(XIN)) oscillation start to be enabled (MR1=0).

For this product, when RAM back-up mode and main clock

(f(XIN)) stop (MR1=1), XIN pin is fixed to “H” in order to avoid the

through current by floating of internal logic. The XIN pin is fixed to

“H” until main clock (f(XIN)) oscillation start to be valid (MR1=0)

by the CMCK instruction from reset state. Accordingly, when an

external clock is used, connect a 1 k

Ω or more resistor to XIN pin

in series to limit of current by competitive signal.

Electric Characteristic Differences Between Mask ROM and One

Time PROM Version MCU

There are differences in electric characteristics, operation mar-

gin, noise immunity, and noise radiation between Mask ROM and

One Time PROM version MCUs due to the difference in the

manufacturing 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.

POF instruction

When the POF 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 ex-

ecuting only the POF instruction.

Be sure to disable interrupts by executing the DI instruction be-

fore executing the EPOF instruction and the POF instruction

continuously.

Program counter

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

built-in ROM.

Power-on reset

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

supply voltage to rise from 0 V to the value of supply voltage or

more 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 RESET pin until the

value of supply voltage reaches the minimum operating voltage.

Clock control

Execute the main clock (f(XIN)) selection instruction (CMCK,

CRCK or CYCK instruction) in the initial setting routine of pro-

gram (executing it in address 0 in page 0 is recommended).

The oscillation circuit by the CMCK, CRCK or CYCK instruction

can be selected only at once. The oscillation circuit correspond-

ing to the first executed one of these instructions is valid.

The CMCK, CRCK, and CYCK instructions can be used only to

select main clock (f(XIN)). In this time, the start of oscillation and

the switch of system clock are not performed.

When the CMCK, CRCK, and CYCK instructions are never ex-

ecuted, main clock (f(XIN)) cannot be used and system can be

operated only by on-chip oscillator.

The no operated clock source (f(RING)) or (f(XIN)) cannot be

used for the system clock. Also, the clock source (f(RING) or

f(XIN)) selected for the system clock cannot be stopped.

On-chip oscillator

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

supply voltage and the operation temperature range.

Be careful that variable frequencies when designing application

products.

When considering the oscillation stabilize wait time at the switch

of clock, be careful that the variable frequency of the on-chip

oscillator clock.

4518 Datasheet(PDF) 77 Page - Renesas Technology Corp

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