GMS81C1102 Datasheet, PDF (59/89 Pages) Hynix Semiconductor – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C1102 / GMS81C1202
(3) Pins AN0/RB0 and AN1/RA1 to AN7/RA7
The analog input pins AN0 to AN7 also function as input/
output port (PORT RA and RB0) pins. When A/D conver-
sion is performed with any of pins AN0 to AN7 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) AV_REF pin input impedance
A series resistor string of approximately 10KΩ is connected be-
tween the AV_REFpin and the V_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_REF pin and the V_SS pin, and
there will be a large reference voltage error.
56
Jan. 2002 ver 2.0