SH7721 datasheet(680/1524 Pages) RENESAS

680 / 1524 page

Section 18

Serial Communication Interface with FIFO (SCIF)

Rev. 3.00 Jan. 18, 2008 Page 618 of 1458

REJ09B0033-0300

In serial transmission, the SCIF operates as described below.

1. When data is written into the transmit FIFO data register (SCFTDR), the SCIF transfers the

data from SCFTDR to the transmit shift register (SCTSR) and starts transmitting. Confirm that

the TDFE flag in the serial status register (SCSSR) is set to 1 before writing transmit data to

SCFTDR. The number of data bytes that can be written is (64 – transmit trigger setting).

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 below the transmit trigger number set in the

FIFO control register (SCFCR), the TDFE flag is set. If the TIE bit in the serial control register

(SCSR) is set to 1 at this time, a transmit-FIFO-data-empty interrupt request is generated.

When the number of transmit data matches the data set in the transmit data stop register

(SCTDSR) while the transmit data stop function is used, the transmit operation is stopped and

the TSF flag in the serial status register (SCSSR) is set. When the TSIE bit in the serial control

interrupt vector is assigned to the transmit-FIFO-data-empty interrupt and the transmit-data-

stop interrupt.

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: 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-bit 1s (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, the TEND flag in the serial status register (SCSSR) is set to 1, the

stop bit is sent, and then the line goes to the mark state in which 1 is output continuously.

SH7721 Datasheet(PDF) 680 Page - Renesas Technology Corp