Datasheet

Table Of Contents
Section 17 Serial Communications Interface 3 (SCI3, IrDA)
Rev. 2.00 Jul. 04, 2007 Page 384 of 692
REJ09B0309-0200
17.4.3 Data Transmission
Figure 17.5 shows an example of operation for transmission in asynchronous mode. In
transmission, the SCI3 operates as described below.
1. The SCI3 monitors the TDRE flag in SSR. If the flag is cleared to 0, the SCI3 recognizes that
data has been written to TDR, and transfers the data from TDR to TSR.
2. After transferring data from TDR to TSR, the SCI3 sets the TDRE flag to 1 and starts
transmission. If the TIE bit in SCR is set to 1 at this time, a TXI3 interrupt request is
generated. Continuous transmission is possible because the TXI3 interrupt routine writes next
transmit data to TDR before transmission of the current transmit data has been completed.
3. The SCI3 checks the TDRE flag at the timing for sending the stop bit.
4. If the TDRE flag is 0, the data is transferred from TDR to TSR, the stop bit is sent, and then
serial transmission of the next frame is started.
5. If the TDRE flag is 1, the TEND flag in SSR is set to 1, the stop bit is sent, and then the “mark
state” is entered, in which 1 is output. If the TEIE bit in SCR is set to 1 at this time, a TEI
interrupt request is generated.
Figure 17.6 shows a sample flowchart for transmission in asynchronous mode.
1 frame
Start
bit
Start
bit
Transmit
data
Transmit
data
Parity
bit
Stop
bit
Parity
bit
Stop
bit
Mar
k
state
1 frame
01D0D1D70/11 110D0D1 D70/1
Serial
data
TDRE
TEND
LSI
operation
TXI3 interrupt
request
generated
TDRE flag
cleared to 0
User
processing
Data written
to TDR
TXI3 interrupt request
generated
TEI3 interrupt request
generated
Figure 17.5 Example SCI3 Operation in Transmission in Asynchronous Mode
(8-Bit Data, Parity, One Stop Bit)