Datasheet

Section 12 Serial Communication Interface (SCI)
Rev.7.00 Feb. 14, 2007 page 466 of 1108
REJ09B0089-0700
Serial data transmission (asynchronous mode): Figure 12.5 shows a sample flowchart for serial
transmission.
The following procedure should be used for serial data transmission.
No
<End>
[1]
Yes
Initialization
Start of transmission
Read TDRE flag in SSR[2]
Write transmit data to TDR
and clear TDRE flag in SSR to 0
No
Yes
No
Yes
Read TEND flag in SSR
[3]
No
Yes
[4]
Clear DR to 0 and
set DDR to 1
Clear TE bit in SCR to 0
TDRE = 1?
All data transmitted?
TEND = 1?
Break output?
[1] SCI initialization:
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] 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 and clear the
TDRE flag to 0.
[3] Serial transmission continuation
procedure:
To cont
inue serial transmission,
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. Checking
and clearing of the TD
RE 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 DDR for the port
corresponding to the TxD pin to 1,
clear DR to 0, then clear the TE bit
in SCR to 0.
Figure 12.5 Sample Serial Transmission Flowchart