SH7125_08 Datasheet, PDF (469/774 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 12 Serial Communication Interface (SCI)
In serial transmission, the SCI operates as described below.
1. The SCI monitors the TDRE flag in the serial status register (SCSSR). If it is cleared to 0, the
SCI recognizes that data has been written to the transmit data register (SCTDR) and transfers
the data from SCTDR to the transmit shift register (SCTSR).
2. After transferring data from SCTDR to SCTSR, the SCI sets the TDRE flag to 1 and starts
transmission. If the TIE bit in the serial control register (SCSCR) is set to 1 at this time, a
transmit-data-empty interrupt (TXI) request is generated.
The serial transmit data is sent from the TXD pin in the following order.
A. Start bit: One-bit 0 is output.
B. Transmit data: 8-bit or 7-bit data is output in LSB-first order.
C. Parity bit or multiprocessor bit: One parity bit (even or odd parity) or one multiprocessor
bit is output. (A format in which neither parity nor multiprocessor bit is 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 SCI checks the TDRE flag at the timing for sending the stop bit.
If the TDRE flag is 0, the data is transferred from SCTDR to SCTSR, the stop bit is sent, and
then serial transmission of the next frame is started.
If the TDRE flag is 1, the TEND flag in SCSSR is set to 1, the stop bit is sent, and then the
"mark state" is entered in which 1 is output. If the TEIE bit in SCSCR is set to 1 at this time, a
TEI interrupt request is generated.
Rev. 4.00 Jul. 25, 2008 Page 449 of 750
REJ09B0243-0400