4507 Datasheet, PDF (50/115 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4507 Group
19 _{Clock control}
Execute the CMCK or the CRCK instruction in the initial setting
routine of program (executing it in address 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.
20 _{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.
21 _{External clock}
When the external signal clock is used as the source oscillation
(f(XIN)), note that the RAM back-up mode (POF2 instructions)
cannot be used.
22 _{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 manufacturing pro-
cesses.
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.
23 _{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.
Rev.3.01 2005.02.04 page 50 of 111
REJ03B0107-0301