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CHAPTER 12 10-BIT A/D CONVERTER (
µ
PD780034AS SUBSERIES)
Preliminary User’s Manual U16035EJ1V0UM
(6) ANI0 to ANI3 pins
These are four analog input pins to input analog signals to undergo A/D conversion to the A/D converter. ANI0
to ANI3 are alternate-function pins that can also be used for digital input.
Cautions 1. Use ANI0 to ANI3 input voltages within the specification range. If a voltage higher than
AV
REF
or lower than AV
SS
is applied (even if within the absolute maximum rating range), the
conversion value of that channel will be undefined and the conversion values of other
channels may also be affected.
2. Analog input (ANI0 to ANI3) pins are alternate function pins that can also be used as input
port (P10 to P13) pins. When A/D conversion is performed by selecting any one of ANI0
to ANI3, do not execute any input instruction to port 1 during conversion. It may cause the
lower conversion resolution.
When a digital pulse is applied to a pin adjacent to the pin in the process of A/D conversion,
A/D conversion values may not be obtained as expected due to coupling noise. Thus, do
not apply any pulse to a pin adjacent to the pin in the process of A/D conversion.
(7) AV
REF
pin
This pin inputs the A/D converter reference voltage.
It converts signals input to ANI0 to ANI3 into digital signals according to the voltage applied between AV
REF
and
AV
SS
.
Caution
A series resistor string of several 10 k
Ω
is connected between the AV
REF
and AV
SS
pins.
Therefore, when output impedance of the reference voltage is too high, it seems as if the AV
REF
pin and the series resistor string are connected in series. This may cause a greater reference
voltage error.
(8) AV
SS
pin
This is the ground potential pin of the A/D converter. Always keep it at the same potential as the V
SS0
or V
SS1
pin when not using the A/D converter.
(9) AV
DD
pin
This is the A/D converter analog power supply pin. Always keep it at the same potential as the V
DD0
or V
DD1
pin
even when not using the A/D converter.
12.3 Registers to Control A/D Converter
The following 4 types of registers are used to control the A/D converter.
• A/D converter mode register 0 (ADM0)
• Analog input channel specification register 0 (ADS0)
• External interrupt rising edge enable register (EGP)
• External interrupt falling edge enable register (EGN)
(1) A/D converter mode register 0 (ADM0)
This register sets the conversion time for analog input to be A/D converted, conversion start/stop, and external
trigger.
ADM0 is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets ADM0 to 00H.
