SH7706 Datasheet, PDF (461/749 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7700 Series

Section 14 Serial Communication Interface (SCI)
In transmitting serial data, the SCI operates as follows:
1. The SCI monitors the TDRE bit in the SCSSR. When TDRE is cleared to 0 the SCI recognizes
that the SCTDR contains new data and loads this data from the SCTDR into the SCTSR.
2. After loading the data from the SCTDR into the SCTSR, the SCI sets the TDRE bit to 1 and
starts transmitting. If the transmit-data-empty interrupt enable bit (TIE) in the SCSCR is set to
1, the SCI requests a transmit-data-empty interrupt (TXI) at this time.
If clock output mode is selected, the SCI outputs eight synchronous clock pulses. If an external
clock source is selected, the SCI outputs data in synchronization with the input clock. Data are
output from the TxD0 pin in order from the LSB (bit 0) to the MSB (bit 7).
3. The SCI checks the TDRE bit when it outputs the MSB (bit 7). If TDRE is 0, the SCI loads
data from the SCTDR into the SCTSR, then begins serial transmission of the next frame. If
TDRE is 1, the SCI sets the TEND bit in the SCSSR to 1, transmits the MSB, then holds the
transmit data pin (TxD0) in the MSB state. If the TEIE in the SCSCR is set to 1, a transmit-end
interrupt (TEI) is requested at this time.
4. After the end of serial transmission, the SCK0 pin is held in the high state.
Figure 14.20 shows an example of SCI transmit operation.
Transfer direction
Synchronization
clock
Serial data
LSB
Bit 0
Bit 1
MSB
Bit 7
Bit 0
Bit 1
Bit 6 Bit 7
TDRE
TEND
TXI interrupt
request
generated
Writes data to TDR
with the TXI interrupt
processing routine
and clears TDRE
bit to 0
TXI interrupt
request
generated
1 frame
Figure 14.20 Example of SCI Transmit Operation
TEI interrupt
request
generated
Rev. 5.00 May 29, 2006 page 413 of 698
REJ09B0146-0500