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CHAPTER 13 A/D CONVERTER
183
(5)
Serial resistor string
The serial resistor string is configured between AV
REF
and AV
SS
. It generates the reference voltages
against which analog inputs are compared.
(6)
ANI0 to ANI7 pins
Pins ANI0 to ANI7 are the 8-channel analog input pins for the A/D converter. They are used to receive the
analog signals for A/D conversion.
Cautions 1. Do not supply pins ANI0 to ANI7 with voltages that fall outside the rated range. If a
voltage greater than AV
REF
or less than AV
SS
(even if within the absolute maximum
rating) is supplied to any of these pins, the conversion value for the corresponding
channel will be undefined. Furthermore, the conversion values for the other channels
may also be affected.
2. The analog input pins (ANI0 to ANI7) also function as input port pins (P60 to P67).
When A/D conversion is performed with any of pins ANI0 to ANI7 selected, be sure not
to execute an instruction that inputs data to port 6 while conversion is in progress, as
this may reduce the conversion resolution.
Also, if digital pulses are applied to a pin adjacent to the pin in the process of A/D
conversion, the expected A/D conversion value may not be obtained due to coupling
noise. Therefore, avoid applying pulses to pins adjacent to the pin undergoing A/D
conversion.
(7)
AV
REF
This pin inputs the A/D converter reference voltage.
It converts signals input to AMI0 to ANI7 into digital signals according to the voltage applied between AV
REF
and AV
SS
.
(8)
AV
SS
pin
The AV
SS
pin is a ground potential pin for the A/D converter. This pin must be held at the same potential as
the V
SS0
pin, even while the A/D converter is not being used.
(9)
AV
DD
pin
The AV
DD
pin is an analog power supply pin for the A/D converter. This pin must be held at the same
potential as the V
DD0
pin, even while the A/D converter is not being used.