GMS81C2020 Datasheet, PDF (65/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

Hyundai Micro Electronics
GMS81C2020/GMS81C2120
(3) Pins AN11/R73 to AN8/R70 and AN7/R67 to AN0/
R60
The analog input pins AN11 to AN0 also function as input/
output port (PORT R7 and R6) pins. When A/D conver-
sion is performed with any of pins AN11 to AN0 selected,
be sure not to execute a PORT input instruction while con-
version 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 applying pulses to pins adjacent to
the pin undergoing A/D conversion.
(4) AVDD pin input impedance
A series resistor string of approximately 10KΩ is connected be-
tween the AVDD pin and the AVSS 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 AVDD pin and the AVSS pin,
and there will be a large reference voltage error.
Nov. 1999 Ver 0.0
preliminary
65