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• Serial data transmission (asynchronous mode)
Figure 16-5 shows a sample flowchart for serial transmission.
The following procedure should be used for serial data transmission.
Initialization
Start transmission
Read TDRE flag in SSR
Write transmit data to TDR
and clear TDRE flag in SSR 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
622
TDRE=1
Yes
Yes
Yes
Yes
<End>
Figure 16-5 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
[2]
enabled.
[2] SCI status check and transmit data
No
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,
No
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
[3]
and clearing of the TDRE flag is
automatic when the DMAC or DTC
is activated by a transmit data
empty interrupt (TXI) request, and
No
date is written to TDR.
[4] Break output at the end of serial
transmission:
To output a break in serial
No
[4]
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.
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