SH7011 Datasheet, PDF (225/292 Pages) Renesas Technology Corp – CMOS single-chip microprocessors

d. Stop bit: one or two 1 bits (stop bits) are output.
e. Marking: output of 1 bits continues until the start bit of the next transmit data.
3. The SCI checks the TDRE bit when it outputs the stop bit. If TDRE is 0, the SCI loads new
data from the TDR into the TSR, outputs the stop bit, then begins serial transmission of the
next frame. If TDRE is 1, the SCI sets the TEND bit to 1 in the SSR, outputs the stop bit, then
continues output of 1 bits (marking). If the transmit-end interrupt enable bit (TEIE) in the SCR
is set to 1, a transmit-end interrupt (TEI) is requested.
Figure 12.5 shows an example of SCI transmit operation.
1
Serial
data
TDRE
Start
bit
0 D0
Parity Stop Start
Data _{bit bit bit}
D1 D7 0/1 1 0 D0
Data
Parity Stop
bit bit
1
D1 D7 0/1 1 ^Idle
(marking
state)
TEND
TxI TxI interrupt
interrupt handler writes
request data in TDR
and clears
TDRE to 0
TxI interrupt
request
1 frame
TEI interrupt request
Figure 12.5 SCI Transmit Operation in Asynchronous Mode (8-Bit Data with Parity and
One Stop Bit)
Receiving Serial Data: Figures 12.6 show a sample flowchart for receiving serial data. The
procedure is as follows (the steps correspond to the numbers in the flowchart).
1. Receive error handling and break detection: If a receive error occurs, read the ORER, PER,
and FER bits of the SSR to identify the error. After executing the necessary error handling,
clear ORER, PER, and FER all to 0. Receiving cannot resume if ORER, PER or FER remain
set to 1. When a framing error occurs, the RxD pin can be read to detect the break state.
2. SCI status check and receive-data read: Read the serial status register (SSR), check that RDRF
is set to 1, then read receive data from the receive data register (RDR) and clear RDRF to 0.
The RxI interrupt can also be used to determine if the RDRF bit has changed from 0 to 1.
3. Continue receiving serial data: Read the RDR and RDRF bit and clear RDRF to 0 before the
stop bit of the current frame is received.
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