GMS81C7216 Datasheet, PDF (57/121 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

(3) AD pin sharing with normal I/O port
The analog input pins AN1 to AN3 also function as input/output
port (PORT R21~R23) pins. When A/D conversion is performed
with any of pins AN1 to AN3 selected, be sure not to execute a
PORT input instruction 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 obtainable due to coupling noise. Therefore, avoid ap-
plying pulses to pins adjacent to the pin undergoing A/D conver-
sion.
(4) AV_DD pin input impedance
A series resistor string of approximately 10kΩ is connected be-
tween the AV_DD pin and the AV_SS pin.
Therefore, if the output impedance of the reference voltage
source is high, this will result in parallel connection to the series
resistor string between the AV_DD pin and the AV_SS pin, and there
will be a large reference voltage error.
GMS81C7208/7216
ENABLE A/D CONVERTER
A/D INPUT CHANNEL SELECT
ANALOG REFERENCE SELECT
A/D START ( ADST = 1 )
NOP
NO
ADSF = 1
YES
READ ADR
Figure 14-3 A/D Converter Operation Flow
ADCM
- R/W - R/W R/W R/W R/W R
7
6
5
4
3
2
1
0
- _{ADEN - ADS2} BATDCSL1 _{ADS0 ADST ADSF}
ADDRESS: 0EC_H
INITIAL VALUE: -0-0 0001_B
A/D status bit
0: A/D conversion is in progress
1: A/D conversion is completed
A/D start bit
0: -
1: A/D start
Setting this bit starts an A/D conversion.
After one cycle, bit is cleared to “0” by hardware.
Analog input channel select
001: Channel 1 (AN1)
010: Channel 2 (AN2)
011: Channel 3 (AN3)
ADR
R R R R RR R R
76543210
BTCL
A/D Conversion Data
A/D converter Enable bit
0: A/D converter module turn off and
current is not flow.
1: Enable A/D converter
ADDRESS: 0ED_H
INITIAL VALUE: Undefined
Figure 14-4 A/D Converter Control Register
FEB. 2005 Ver 1.04
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