Figure 12.7 Sample Serial Transmission Flowchart - Renesas H8S/2111B Hardware Manual

Initialization
Start transmission
Read TDRE flag in SSR
TDRE = 1
Yes
Write transmit data to TDR
and clear TDRE flag in SSR to 0
All data transmitted?
Yes
Read TEND flag in SSR
TEND = 1
Yes
Break output?
Yes
Clear DR to 0 and
set DDR to 1
Clear TE bit in SCR to 0
<End>

Figure 12.7 Sample Serial Transmission Flowchart

[1] SCI initialization:
[1]
The TxD pin is automatically designated
as the transmit data output pin.
After the TE bit is set to 1, a frame of 1s
is output, and transmission is enabled.
[2]
[2] SCI status check and transmit data
write:
Read SSR and check that the TDRE flag
No
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, read 1
from the TDRE flag to confirm that
writing is possible, then write data to
No
TDR, and clear the TDRE flag to 0.
[4] Break output at the end of serial
transmission:
To output a break in serial transmission,
[3]
set DDR for the port corresponding to
the TxD pin to 1, clear DR to 0, then
clear the TE bit in SCR to 0.
No
No
[4]
Rev. 1.00, 05/04, page 255 of 544