M306H7MG-XXXFP Datasheet, PDF (179/329 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with DATA ACQUISITION CONTROLLER

M306H7MG-XXXFP/MC-XXXFP/FGFP
12. A/D CONVERTER
12.11 Caution of Using A/D Converter
(1) Make sure the port direction bits for those pins that are used as analog inputs are set to “0” (input mode).
Also, if the ADCON0 register’s TGR bit = 1 (external trigger), make sure the port direction bit for the
ADTRG pin is set to “0” (input mode).
(2) 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)) each and the AVSS pin.
Similarly, insert a capacitor between the VCC pin and the VSS pin. Figure 12.11 is an example connection of
each pin.
(3) If the CPU reads the ADi register (i = 0 to 7) at the same time the conversion result is stored in the ADi
register after completion of A/D conversion, an incorrect value may be stored in the ADi register. This
problem occurs when a divide-by-n clock derived from the main clock or a subclock is selected for CPU
clock.
•When operating in one-shot or single-sweep mode
Check to see that A/D conversion is completed before reading the target ADi register. (Check the IR bit in
the ADIC register to see if A/D conversion is completed.)
•When operating in repeat mode or repeat sweep mode 0 or 1
Use the main clock for CPU clock directly without dividing it.
(4) If A/D conversion is forcibly terminated while in progress by setting the ADCON0 register’s ADST bit to
“0” (A/D conversion halted), the conversion result of the A/D converter is indeterminate. The contents of
ADi registers irrelevant to A/D conversion may also become indeterminate. If while A/D conversion is
underway the ADST bit is cleared to “0” in a program, ignore the values of all ADi registers.
Microcomputer
VCC1
VCC1 (16 pin) AV CC
C4
VSS
VCC2
C5
AV SS
VCC2 (62 pin)
C3
ANi
VSS
VCC2
C2
ANi: ANi (i=0 to 7)
Note 1: C1≥0.47µF, C2 ≥0.47µF, C3 ≥100pF, C4 ≥0.1µF, C5≥0.1µF (reference)
Note 2: Use thick and shortest possible wiring to connect capacitors.
Figure 12.11 VCC, VSS, AVCC, AVSS, VREF and ANi Connection
Rev.2.10 Oct 25, 2006 Page 179 of 326
REJ03B0152-0210