M16CSLASH1N datasheet(224/238 Pages) RENESAS

224 / 238 page

Rev.1.00

Oct 20, 2004

page 212 of 222

M16C/1N Group

REJ090007-0100Z

20. Precautionary Notes in Using the Device

20.5 A/D Converter

1. Only write to each bit (except bit 6) of the AD Control Register 0, or each bit of the AD Control

occurs). When the VREF connection bit is changed from "0" to "1", wait 1 µs or longer before

starting AD conversion.

2. To prevent noise-induced device malfunction or latchup, as well as to reduce conversion errors,

insert capacitors between the VCC, VREF, and analog input pins (ANi) each and the VSS pin. Figure

20.1 shows an example connection of each pin.

3. Make sure the port direction bits for those pins that are used as analog inputs are set to "0" (input

mode).

____

When setting the KIi input enable bit to "1" (Enabled) to use key input interrupt and using AN8 to

AN11 as analog input pins, be careful about the following points.

• A key input interrupt request is generated when the A/D input voltage goes "LOW".

• If the A/D input voltage approaches 1/2 VCC, power supply current may increase due to pass

____

current on schmitt circuit of key input interrupt. (When setting the KIi input enable bit to "0"

(Disabled), pass current doesn't flow.)

5. The ØAD frequency must be 10 MHz or less. Without sample-and-hold function, limit the ØAD

frequency to 250 kHz or more. With the sample and hold function, limit the ØAD frequency to 1 MHz

or more.

Figure 20.1 Example connection of each pin

Note 1: C1

≥0.47µF, C2≥0.47µF, C3≥100pF (reference).

Note 2: Use thick and shortest possible wiring to connect capacitors.

Microcomputer

VREF

VCC

VSS

ANi

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