HMS87C1808B Datasheet, PDF (62/99 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

HMS87C1X04B/08B/16B
port (PORT RA and RB0) pins. When A/D conversion is per-
formed with any of pins AN0 to AN7 selected, be sure not to ex-
ecute 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) AVref pin input impedance
A series resistor string of approximately 10KΩ is connected be-
tween the AVref pin and the VSS 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 AVref pin and the VSS pin, and there
will be a large reference voltage error.
58
SEP. 2004 Ver 1.03