Renesas Hitachi H8S/2191, Hardware Manual

Page: 499 / 1065

Rev. 2.0, 11/00, page 472 of 1037
(b) Serial Data Transmission (Asynchronous Mode)
Figure 23.5 shows a sample flowchart for serial transmission.
The following procedure should be used for serial data transmission.
No
< End >
[1]
Yes
Initialization
Start transmission
Read TDRE flag in SSR1 [1]
Write transmit data to TDR1 and
clear TDRE flag in SSR1 to 0
No
Yes
No
Yes
Read TEND flag in SSR1
[3]
No
Yes
[4]
Clear PDR to 0
and set PCR to 1
Clear TE bit in SCR1 to 0
TDRE=1
All data transmitted?
TEND=1
Break output?
SCI1 initialization:
The SO1 pin is automatically designated as
the transmit data output pin.
SCI1 status check and transmit data write:
Read SSR1 and check that the TDRE flag
is set to 1, then write transmit data to TDR1
and clear the TDRE flag to 0.
Serial transmission continuation procedure:
To continue serial transmission, read 1
from the TDRE flag to confirm that writing is
possible, then write data to TDR1, and then
clear the TDRE flag to 0.
Break output at the end of serial
transmission:
To output a break in serial transmission, set
PCR for the port corresponding to the SO1
pin to 1, clear PDR to 0, then clear the TE
bit in SCR1 to 0.
[1]
[2]
[3]
[4]
Figure 23.5 Sample Serial Transmission Flowchart