Figure 15.17 Sample Serial Transmission Flowchart - Renesas H8S Series Hardware Manual

Section 15 Serial Communication Interface (SCI, IrDA)
Initialization
Start transmission
Read TDRE flag in SSR
TDRE = 1
Write transmit data to TDR and
clear TDRE flag in SSR to 0
All data transmitted?
Read TEND flag in SSR
TEND = 1
Clear TE bit in SCR to 0
<End>
Rev. 3.00 Jul. 14, 2005 Page 476 of 986
REJ09B0098-0300
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Yes
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Figure 15.17 Sample Serial Transmission Flowchart

[1] SCI initialization:
[1]
The TxD pin is automatically
designated as the transmit data output
pin.
[2] SCI status check and transmit data
[2]
write:
Read SSR and check that the TDRE
flag is set to 1, then write transmit data
to TDR and clear the TDRE flag to 0.
[3] Serial transmission continuation
procedure:
To continue serial transmission, be
sure to read 1 from the TDRE flag to
confirm that writing is possible, then
write data to TDR, and then clear the
TDRE flag to 0.
However, the TDRE flag is checked
[3]
and cleared automatically when the
DTC is initiated by a transmit data
empty interrupt (TXI) request and
writes data to TDR.