Renesas SH7781 - Manual (Page 1109)

21. Serial Communication Interface with FIFO (SCIF)
Rev.1.00 Jan. 10, 2008 Page 1079 of 1658
REJ09B0261-0100
In serial transmission, the SCIF operates as follows.
1. When data is written to SCFTDR, the SCIF transfers the data from SCFTDR to SCTSR and
starts transmission. Confirm that the TDFE flag in SCFSR is set to 1 before writing transmit
data to SCFTDR. The number of data bytes that can be written is at least 64
− (transmit trigger
setting count).
2. When data is transferred from SCFTDR to SCTSR and transmission is started, consecutive
transmit operations are performed until there is no transmit data left in SCFTDR. When the
number of transmit data bytes in SCFTDR falls to or below the transmit trigger count set in
SCFCR, the TDFE flag is set. If the TIE bit in SCSCR 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 SCIF_TXD 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 SCFTDR transmit data at the timing for sending the stop bit. If data is
present, the data is transferred from SCFTDR to SCTSR, the stop bit is sent, and then serial
transmission of the next frame is started.
If there is no transmit data after the stop bit is sent, the TEND flag in SCFSR is set to 1, and
then the SCIF goes to the mark state in which 1 is output from the SCIF_TXD pin.