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In serial transmission, the SCIF operates as described below.
1. When data is written into SCFTDR2, the SCIF transfers the data from SCFTDR2 to SCTSR2
and starts transmitting. Confirm that the TDFE flag in the serial status register (SCFSR2) is set
to 1 before writing transmit data to SCFTDR2. The number of data bytes that can be written is
at least (16 - transmit trigger setting).
2. When data is transferred from SCFTDR2 to SCTSR2 and transmission is started, consecutive
transmit operations are performed until there is no transmit data left in SCFTDR2. When the
number of transmit data bytes in SCFTDR2 falls to or below the transmit trigger number set in
the FIFO control register (SCFCR2), the TDFE flag is set. If the TIE bit in SCSCR2 is set to 1
at this time, a transmit-FIFO-data-empty interrupt (TXI) request is generated.
The serial transmit data is sent from the TxD2 pin in the following order.
a. Start bit: One 0-bit is output.
b. Transmit data: 8-bit or 7-bit data is output in LSB-first order.
c. Parity bit: One parity bit (even or odd parity) is output. (A format in which a parity bit is
not output can also be selected.)
d. Stop bit(s): One or two 1-bits (stop bits) are output.
e. Mark state: 1 is output continuously until the start bit that starts the next transmission is
sent.
3. The SCIF checks the SCFTDR2 transmit data at the timing for sending the stop bit. If data is
present, the data is transferred from SCFTDR2 to SCTSR2, the stop bit is sent, and then serial
transmission of the next frame is started.
If there is no transmit data, the TEND flag in SCFSR2 is set to 1, the stop bit is sent, and then
the line goes to the mark state in which 1 is output.
Figure 16.9 shows an example of the operation for transmission in asynchronous mode.
Rev. 4.0, 04/00, page 600 of 850
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