SH7101 datasheet(361/560 Pages) RENESAS

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Section 10 Serial Communication Interface (SCI)

Rev.1.00 Sep. 18, 2008 Page 327 of 522

REJ09B0069-0100

10.8

Usage Notes

10.8.1

TDR Write and TDRE Flag

The TDRE bit in the serial status register (SSR) is a status flag indicating transferring of transmit

data from TDR into TSR. The SCI sets the TDRE bit to 1 when it transfers data from TDR to

TSR.

Data can be written to TDR regardless of the TDRE bit status.

If new data is written in TDR when the TDRE bit is 0, however, the old data stored in TDR will be

lost because the data has not yet been transferred to TSR. Before writing transmit data to TDR, be

sure to check that the TDRE bit is set to 1.

10.8.2

Module Standby Mode Setting

SCI operation can be disabled or enabled using the module standby control register. The initial

setting is for SCI operation to be halted. Register access is enabled by clearing module standby

mode. For details, refer to section 18, Power-Down Modes.

10.8.3

Break Detection and Processing (Asynchronous Mode Only)

When framing error detection is performed, a break can be detected by reading the RxD pin value

directly. In a break, the input from the RxD pin becomes all 0s, and so the FER flag is set, and the

PER flag may also be set. Note that, since the SCI continues the receive operation after receiving

a break, even if the FER flag is cleared to 0, it will be set to 1 again.

10.8.4

Sending Break Signal (Asynchronous Mode Only)

The TxD pin becomes of the I/O port general I/O pin with the I/O direction and level determined

by the port data register (DR) and the port I/O register (IOR) of the pin function controller (PFC).

These conditions allow break signals to be sent.

The DR value is substituted for the marking status until the PFC is set. Consequently, the output

port is set to initially output a 1.

To send a break in serial transmission, first clear the DR to 0, then establish the TxD pin as an

output port using the PFC.

When the TE bit is cleared to 0, the transmission section is initialized regardless of the present

transmission status.

SH7101 Datasheet(PDF) 361 Page - Renesas Technology Corp