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M16C/62P Group (M16C/62P, M16C/62PT)
24.11 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, AN2_i) each and the AVSS pin.
Similarly, insert a capacitor between the VCC1 pin and the VSS pin. Figure 24.4 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 12MHz 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 operating mode, select analog input pin again in the CH2 to CH0 bits in the ADCON0
register and the SCAN1 to SCAN0 bits in the ADCON1 register.
ANi: ANi, AN0_i and AN2_i (i=0 to 7)
NOTES :
Figure 24.4
Use of Capacitors to Reduce Noise
Rev.2.41
Jan 10, 2006
REJ09B0185-0241
http://www.xinpian.net
Microcomputer
VCC1
VCC1
C4
VSS
VCC2
VCC2
C5
VSS
1. C1 ≥ 0.47 µ F, C2 ≥ 0.47 µ F, C3 ≥ 100pF, C4 ≥ 0.1 µ F, C5 ≥ 0.1 µ F (reference)
2. Use thick and shortest possible wiring to connect capacitors.
Page 375 of 390
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VCC1
AVCC
VREF
C2
C1
AVSS
C3
ANi
24. Precautions
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