M16C30P_07 Datasheet, PDF (297/317 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/30 SERIES

M16C/30P Group
22. Usage Precaution
22.10 A/D Converter
Set ADCON0 (except bit 6), ADCON1 and ADCON2 registers when A/D conversion is stopped (before a trigger
occurs).
When the VCUT bit in the ADCON1 register is changed from “0” (Vref not connected) to “1” (Vref connected),
start A/D conversion after passing 1 μs or longer.
To prevent noise-induced device malfunction or latchup, as well as to reduce conversion errors, insert capacitors
between the AVCC, VREF, and analog input pins (ANi(i=0 to 7), AN0_i) each and the AVSS pin. Similarly, insert
a capacitor between the VCC1 pin and the VSS pin. Figure 22.3 is an example connection of each pin.
Make sure the port direction bits for those pins that are used as analog inputs are set to “0” (input mode).
Also, if the TGR bit in the ADCON0 register = 1 (external trigger), make sure the port direction bit for the ADTRG
pin is set to “0” (input mode).
When using key input interrupts, do not use any of the four AN4 to AN7 pins as analog inputs. (A key input
interrupt request is generated when the A/D input voltage goes low.)
The φAD frequency must be 10MHz or less. Without sample-and-hold function, limit the φAD frequency to
250kHz or more. With the sample and hold function, limit the φAD frequency to 1MHz or more.
When changing an A/D operation mode, select analog input pin again in the CH2 to CH0 bits in the ADCON0
register.
VCC1
C4
VCC1
C5
Microcomputer
VCC1 AVCC
VSS
VCC2
VSS
VREF
C1
AVSS
ANi
VCC1
C2
C3
ANi: ANi, AN0_i (i=0 to 7)
NOTES :
1. C1≥0.47μF, C2≥0.47μF, C3≥100pF, C4≥0.1μF, C5≥0.1μF (reference)
2. Use thick and shortest possible wiring to connect capacitors.
Figure 22.3 Use of Capacitors to Reduce Noise
Rev.1.22 Mar 29, 2007 Page 281 of 291
REJ09B0179-0122