7733 datasheet(611/940 Pages) RENESAS

611 / 940 page

7733 Group User’s Manual

21-63

APPENDIX

(4) Wiring to pin CNVss

[In single-chip and memory expansion modes]

q Connect pin CNVss to pin Vss of the microcomputer with the shortest possible wiring.

q If the above countermeasure cannot be taken, insert an approximate 5 k

Ω resistor between pins

CNVss and Vss and, again, make the distance between the resistor and pin CNVss as short as

possible.

[In microprocessor mode]

q Connect pin CNVss to pin Vcc with the shortest possible wiring.

Reason

Pin CNVss is connected to the internal ROM in the low-impedance state. (Noise is easily to be fed

to the pin in this condition.)

If noise enters pin CNVss, incorrect instruction codes or data are fetched from the built-in PROM. This

may cause a program runaway.

Fig. 15 Built-in PROM version: Wiring for pin CNVss

Microprocessor mode

CNVSS

VCC

Shortest possible wiring

Approx. 5 K

Ω

Pin CNVss is connected to pin Vss

with the shortest possible wiring.

CNVSS

VSS

Single-chip and

Memory expansion modes

M37733EHBXXXFP

g The above countermeasure is not necessary for pin BYTE.

M37733EHBXXXFP

Pin CNVss is connected to pin Vcc

with the shortest possible wiring.

Shortest possible wiring

Appendix 8. Countermeasure examples against noise

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