Hitachi H8S/2646 Hardware Manual page 506

Initialization
Start transmission
Read TDRE flag in SSR
TDRE= 1
Write transmit data to TDR and
set MPBT bit in SSR
Clear TDRE flag to 0
All data transmitted?
Read TEND flag in SSR
TEND= 1
Break output?
Clear DR to 0 and set DDR to 1
Clear TE bit in SCR to 0
<End>
Figure 13-10 Sample Multiprocessor Serial Transmission Flowchart
474
No
Yes
No
Yes
No
Yes
No
Yes
[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
[2]
transmission is enabled.
[2]
SCI status check and transmit
data write:
Read SSR and check that the
TDRE flag is set to 1, then write
transmit data to TDR. Set the
MPBT bit in SSR to 0 or 1.
Finally, 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
[3]
possible, then write data to TDR,
and then clear the TDRE flag to
0. Checking and clearing of the
TDRE flag is automatic when the
DTC is activated by a transmit
data empty interrupt (TXI)
request, and data is written to
TDR.
[4]
Break output at the end of serial
transmission:
To output a break in serial
transmission, set the port DDR to
[4]
1, clear DR to 0, then clear the
TE bit in SCR to 0.