Hardware manual

Microcomputer Technical Q&A
101
Q&A No.: QAH8S-226
Category: SCI
Subject: Difference between TDRE Flag and TEND Flag
Question
What is the difference between the TDRE flag and TEND flag in the serial status register (SSR)?
Answer
The TDRE flag indicates that the transmit data register (TDR) is in the write-enabled state,
without regard to the internal state of the transmit shift register (TSR).
The TEND flag indicates that TSR is empty, and TDR is in the write-enabled state. The status of
the TEND flag should be checked to confirm whether all data has been transmitted.
TDR TDR
TSR
TSR
TDRE generation state
TEND generation state
(Empty) (Empty)
(Empty)
Data
TDRE and TEND Generation States
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 — — — —