Hardware manual

Microcomputer Technical Q&A
137
Q&A No.: QAH8S-249
Category: I/O Ports
Subject: Port 3 Open-Drain Output
Question
Port 3 pins are multiplexed as SCI0 and SCI1 input/output pins. Can port 3 pins be used as open-
drain outputs only when the I/O port function is used, or also when the SCI output pin function is
used?
Answer
Open-drain output is also possible when port 3 pins are used as SCI output pins.
In both I/O port operation and SCI output pin operation, open-drain output can be selected by
setting port 3 open-drain control register (P3ODR) bits to 1. After making the P3ODR setting, set
the relevant pins to output mode.
Note: When open-drain output is used, it is still necessary to ensure that the relevant pin levels
do not exceed the input voltage range values specified in the Electrical Characteristics
section.
Applicable Products
Applicability Series Applicability Series Applicability Series
Entire H8S Series Yes H8S/2655 Yes H8S/2350
Yes H8S/2355 Yes H8S/2357 Yes H8S/2345
Yes H8S/2245 H8S/2148 H8S/2144
H8S/2138 H8S/2134 H8S/2128
H8S/2124 — — — —