Hitachi SH7750 Hardware Manual page 695

Serial Data Transmission (Synchronous Mode): Figure 15.19 shows a sample flowchart for
serial transmission.
Use the following procedure for serial data transmission after enabling the SCI for transmission.
Start of transmission
Read TDRE flag in SCSSR1
TDRE = 1?
Write transmit data to SCTDR1
and clear TDRE flag
in SCSSR1 to 0
All data transmitted?
Read TEND flag in SCSSR1
TEND = 1?
Clear TE bit in SCSCR1 to 0
No
Yes
No
Yes
No
Yes
End
Figure 15.19 Sample Serial Transmission Flowchart
1. SCI status check and transmit
data write: Read SCSSR1 and
check that the TDRE flag is set to
1, then write transmit data to
SCTDR1 and clear the TDRE flag
to 0.
2. To continue serial transmission,
be sure to read 1 from the TDRE
flag to confirm that writing is
possible, then write data to
SCTDR1, and then clear the
TDRE flag to 0. (Checking and
clearing of the TDRE flag is
automatic when the direct
memory access controller
(DMAC) is activated by a
transmit-data-empty interrupt
(TXI) request, and data is written
to SCTDR1.)
Rev. 6.0, 07/02, page 645 of 986