4513 datasheet(193/210 Pages) RENESAS

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3-26

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.

q When the VPP pin is also used as the

CNVSS pin

Connect an approximately 5 k

Ω resistor to

the VPP pin the shortest possible in series

and also to the V SS 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 k

Ω resistor is used in the

Mask ROM version, the microcomputer

operates correctly.

q 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

VSS

In the shortest

distance

Approximately

Ω

3.4.2 Connection of bypass capacitor across VSS

line and VDD line

Connect an approximately 0.1

µF 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.

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