SH7046 Datasheet, PDF (389/611 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7046 Series

Section 12 Serial Communication Interface (SCI)
12.4.5 Data transmission (Asynchronous mode)
Figure 12.6 shows an example of the operation for transmission in asynchronous mode. In
transmission, the SCI operates as described below.
1. The SCI monitors the TDRE flag in SSR, and if is cleared to 0, 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 SCI sets the TDRE flag to 1 and starts
transmission. If the TIE bit is set to 1 at this time, a transmit data empty interrupt request
(TXI) is generated. Because the TXI interrupt routine writes the next transmit data to TDR
before transmission of the current transmit data has finished, continuous transmission can be
enabled.
3. Data is sent from the TxD pin in the following order: start bit, transmit data, parity bit or
multiprocessor bit (may be omitted depending on the format), and stop bit.
4. The SCI checks the TDRE flag at the timing for sending the stop bit.
5. 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.
6. 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 12.7 shows a sample flowchart for transmission in asynchronous mode.
Start
1 bit
Data
Parity Stop Start
bit bit bit
Data
Parity Stop
bit bit 1
TxD
0 D0 D1
D7 0/1 1 0 D0 D1
D7 0/1 1 ^{Idle state}
(mark state)
TDRE
TEND
TXI interrupt
request
generated
Data written to TDR
and TDRE flag cleared
to 0 in TXI interrupt
processing routine
frame
TXI interrupt
request
generated
TEI interrupt
request
generated
Figure 12.6 Example of Operation in Transmission in Asynchronous Mode
(Example with 8-Bit Data, Parity, One Stop Bit)
Rev. 4.00 Dec 05, 2005 page 345 of 564
REJ09B0270-0400