Hardware manual

Microcomputer Technical Q&A
104
Q&A No.: QAH8S-229
Category: SCI
Subject: Transmit/Receive Operation in Synchronous Mode
Question
Can reception alone be performed in transmit/receive operation (TE = RE = 1) in synchronous
mode?
Answer
As the same clock is used for transmission and reception in synchronous mode, transmission and
reception are performed simultaneously in transmit/receive operation (TE = RE = 1).
Consequently, transmit/receive operation cannot be performed until transmission is started (TDRE
is cleared to 0).
When the H8S Series chip performs clock output, when TDRE is cleared to 0 the clock is output
and transmission and reception are performed simultaneously.
When the H8S Series chip uses clock input, TDRE should be cleared to 0 before inputting the
clock. The clock will be ignored if input before TDRE is cleared to 0.
To perform reception only, write dummy data to TDR to clear TDRE to 0.
Applicable Products
Applicability Series Applicability Series Applicability Series
Yes Entire H8S Series H8S/2655 H8S/2350
H8S/2355 H8S/2357 H8S/2345
H8S/2245 H8S/2148 H8S/2144
H8S/2138 H8S/2134 H8S/2128
H8S/2124 — — — —