M16C1N Datasheet, PDF (224/238 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/10 SERIES

M16C/1N Group
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
Register 1, or bit 0 of the AD Control Register 2 when AD conversion is stopped (before a trigger
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.
Microcomputer
VCC
VREF
C1
C2
VSS
C3
ANi
Note 1: C1≥0.47µF, C2≥0.47µF, C3≥100pF (reference).
Note 2: Use thick and shortest possible wiring to connect capacitors.
Figure 20.1 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).
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4. 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
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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.
Rev.1.00 Oct 20, 2004 page 212 of 222
REJ090007-0100Z