Hitachi SH7032 Hardware Manual page 430

If clock output is selected, the SCI outputs eight serial clock pulses. If an external clock source
is selected, the SCI outputs data in synchronization with the input clock. Data is output from
the TxD 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 TDR into TSR, transmits the MSB, then begins serial transmission of the next frame.
If TDRE is 1, the SCI sets the TEND bit in SSR to 1, transmits the MSB, then holds the
transmit data pin (TxD) in the MSB state. If the transmit-end interrupt enable bit (TEIE) in
SCR is set to 1, a transmit-end interrupt (TEI) is requested at this time.
4. After the end of serial transmission, the SCK pin is held in the high state.
Transmit direction
Serial clock
Serial data
TDRE
TEND
TXI
request
Transmitting and Receiving Data: SCI Initialization (Synchronous Mode): Before transmitting
or receiving, software must clear the TE and RE bits to 0 in the serial control register (SCR), then
initialize the SCI as follows.
When changing the communication mode or format, always clear the TE and RE bits to 0 before
following the procedure given below. Clearing TE to 0 sets TDRE to 1 and initializes the transmit
shift register (TSR). Clearing RE to 0, however, does not initialize the RDRF, PER, FER, and
ORER flags and receive data register (RDR), which retain their previous contents.
Figure 13.16 shows a sample flowchart for initializing the SCI.
LSB
Bit 0 Bit 1
TXI interrupt
handler writes
data in TDR and
clears TDRE to 0
1 frame
Figure 13.15 Example of SCI Transmit Operation
MSB
Bit 7 Bit 0 Bit 1
TXI
request
Bit 6 Bit 7
TEI
request
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