HD64F2357VF13 Datasheet, PDF (538/1049 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

In serial transmission, the SCI operates as described below.
[1] The SCI monitors the TDRE flag in SSR, and if is 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 (TXI) is generated.
When clock output mode has been set, the SCI outputs 8 serial clock pulses. When use of an external clock has been
specified, data is output synchronized with the input clock.
The serial transmit data is sent from the TxD pin starting with the LSB (bit 0) and ending with the MSB (bit 7).
[3] The SCI checks the TDRE flag at the timing for sending the MSB (bit 7).
If the TDRE flag is cleared to 0, data is transferred from TDR to TSR, and serial transmission of the next frame is
started.
If the TDRE flag is set to 1, the TEND flag in SSR is set to 1, the MSB (bit 7) is sent, and the TxD pin maintains its
state.
If the TEIE bit in SCR is set to 1 at this time, a TEI interrupt request is generated.
[4] After completion of serial transmission, the SCK pin is fixed.
Figure 14-17 shows an example of SCI operation in transmission.
Serial clock
Transfer direction
Serial data
Bit 7 Bit 0
Bit 7 Bit 0 Bit 1
TDRE
TEND
TXI interrupt
Data written to TDR
request generated and TDRE flag
cleared to 0 in TXI
interrupt service routine
TXI interrupt
request generated
1 frame
Bit 6 Bit 7
TEI interrupt
request generated
Figure 14-17 Example of SCI Operation in Transmission
Rev.6.00 Oct.28.2004 page 508 of 1016
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