HD64F38602R Datasheet, PDF (298/552 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 14 Serial Communication Interface 3 (SCI3, IrDA)
14.5.3 Serial Data Transmission
Figure 14.10 shows an example of SCI3 operation for transmission in clock synchronous mode.
In serial transmission, the SCI3 operates as described below.
1. The SCI3 monitors the TDRE flag in SSR, and if the flag is 0, the SCI3 recognizes that data
has been written to TDR, and transfers the data from TDR to TSR.
2. 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.
3. 8-bit data is sent from the TXD3 pin synchronized with the output clock when output clock
mode has been specified, and synchronized with the input clock when use of an external clock
has been specified. Serial data is transmitted sequentially from the LSB (bit 0), from the TXD3
pin.
4. The SCI3 checks the TDRE flag at the timing for sending the MSB (bit 7).
5. If the TDRE flag is cleared to 0, data is transferred from TDR to TSR, and serial transmission
of the next frame is started.
6. If the TDRE flag is set to 1, the TEND flag in SSR is set to 1, and the TDRE flag maintains
the output state of the last bit. If the TEIE bit in SCR is set to 1 at this time, a TEI3 interrupt
request is generated.
7. The SCK3 pin is fixed high.
Figure 14.11 shows a sample flowchart for serial data transmission. Even if the TDRE flag is
cleared to 0, transmission will not start while a receive error flag (OER, FER, or PER) is set to 1.
Make sure that the receive error flags are cleared to 0 before starting transmission.
Serial
clock
Serial
data
TDRE
TEND
Bit 0 Bit 1
1 frame
Bit 7
Bit 0
Bit 1
Bit 6
1 frame
Bit 7
LSI
TXI3
operation interrupt
request
User
generated
processing
TDRE flag
cleared
to 0
TXI3 interrupt request
generated
Data written
to TDR
TEI3 interrupt request
generated
Figure 14.10 Example of SCI3 Operation in Transmission in Clock Synchronous Mode
Rev. 3.00 May 15, 2007 Page 266 of 516
REJ09B0152-0300