Data Transmission; Figure 14.6 Example Of Sci3 Transmission In Asynchronous Mode (8-Bit Data, Parity, One Stop Bit) - Renesas H8 Series Hardware Manual

Section 14 Serial Communication Interface 3 (SCI3)
14.4.3

Data Transmission

Figure 14.6 shows an example of operation for transmission in asynchronous mode. In
transmission, SCI3 operates as described below.
1. SCI3 monitors the TDRE flag in SSR. If the flag is cleared to 0, 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, SCI3 sets the TDRE flag to 1 and starts
transmission. If the TIE bit is set to 1 at this time, a TXI interrupt request is generated.
Continuous transmission is possible because the TXI interrupt routine writes next transmit data
to TDR before transmission of the current transmit data has been completed.
3. 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 SCR3 is set to 1 at this time, a TEI
interrupt request is generated.
6. Figure 14.7 shows a sample flowchart for transmission in asynchronous mode.
Start
bit
Serial
1 0
data
TDRE
TEND
LSI TXI interrupt
operation request
generated
User
processing
Figure 14.6 Example of SCI3 Transmission in Asynchronous Mode
Rev. 3.00 Sep. 14, 2006 Page 214 of 408
REJ09B0105-0300
Transmit Parity
data bit
D0 D1 D7 0/1
1 frame
TDRE flag TXI interrupt request generated
cleared to 0
Data written
to TDR
(8-Bit Data, Parity, One Stop Bit)
Stop Start Transmit
bit bit data
1 0 D0 D1
1 frame
Parity Stop Mark
bit bit state
D7 0/1 1 1
TEI interrupt request
generated