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APPENDIX
3.4 Notes on noise
4513/4514 Group User’s Manual
(5) Wiring to VPP pin of One Time PROM version
In the built-in PROM version of the 4513/4514
Group, the CNVSS pin is also used as the
built-in PROM power supply input pin VPP.
● When the VPP pin is also used as the
CNVSS pin
Connect an approximately 5 kΩ resistor to
the VPP pin the shortest possible in series
and also to the VSS pin. When not
connecting the resistor, make the length of
wiring between the VPP pin and the VSS
pin the shortest possible (refer to Figure
3.4.5)
Note: Even when a circuit which included an
approximately 5 kΩ resistor is used in the
Mask ROM version, the microcomputer
operates correctly.
● Reason
The VPP pin of the One Time PROM ver-
sion is the power source input pin for the
built-in PROM. When programming in the
built-in PROM, the impedance of the VPP
pin is low to allow the electric current for
writing flow into the PROM. Because of
this, noise can enter easily. If noise enters
the VPP pin, abnormal instruction codes or
data are read from the built-in PROM, which
may cause a program runaway.
Fig. 3.4.5 Wiring for the VPP pin of the One Time
PROM version
CNVSS/VPP
When the VPP pin is also used as the CNVSS pin
V
SS
In the shortest
distance
Approximately
5kΩ
3.4.2 Connection of bypass capacitor across VSS
line and VDD line
Connect an approximately 0.1
µ
F bypass capacitor
across the VSS line and the VDD line as follows:
• Connect a bypass capacitor across the VSS pin
and the VDD pin at equal length.
• Connect a bypass capacitor across the VSS pin
and the VDD pin with the shortest possible wiring.
• Use lines with a larger diameter than other signal
lines for VSS line and VDD line.
• Connect the power source wiring via a bypass
capacitor to the VSS pin and the VDD pin.
Fig. 3.4.6 Bypass capacitor across the VSS line
and the VDD line
VSS
VDD
VSS
VDD
N.G. O.K.