M37544 Datasheet, PDF (66/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7544 Group
Electric Characteristic Differences Among
Mask ROM and One Time PROM Version
MCUs
There are differences in electric characteristics, operation margin,
noise immunity, and noise radiation among mask ROM and One
Time PROM version MCUs due to the differences in the manufac-
turing processes.
When manufacturing an application system with One Time PROM
version and then switching to use of the mask ROM version, per-
form 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.
NOTES ON HARDWARE
Handling of Power Source Pin
In order to avoid a latch-up occurrence, connect a capacitor suit-
able for high frequencies as bypass capacitor between power
source pin (Vcc pin) and GND pin (Vss pin). Besides, connect the
capacitor to as close as possible. For bypass capacitor which
should not be located too far from the pins to be connected, a ce-
ramic capacitor of 0.01 µF to 0.1 µF is recommended.
One Time PROM Version
The CNVss pin is connected to the internal memory circuit block
by a low-ohmic resistance, since it has the multiplexed function to
be a programmable power source pin (VPP pin) as well.
To improve the noise reduction, connect a track between CNVss
pin and Vss pin with 1 to 10 kΩ resistance.
The mask ROM version track of CNVss pin has no operational in-
terference even if it is connected via a resistor.
Rev.1.04 2004.06.08 page 66 of 66
REJ03B0012-0104Z