HD64F2149YV datasheet(517/1075 Pages) RENESAS

517 / 1075 page

Section 15 Serial Communication Interface (SCI, IrDA)

Rev. 3.00 Jan 18, 2006 page 489 of 1044

REJ09B0280-0300

Break Detection and Processing: When a framing error (FER) is detected, 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 parity error flag (PER) 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.

Sending a Break: The TxD pin has a dual function as an I/O port whose direction (input or

output) is determined by DR and DDR. This feature can be used to send a break.

Between serial transmission initialization and setting of the TE bit to 1, the mark state is replaced

by the value of DR (the pin does not function as the TxD pin until the TE bit is set to 1).

Consequently, DDR and DR for the port corresponding to the TxD pin should first be set to 1.

To send a break during serial transmission, first clear DR to 0, then clear the TE bit to 0.

When the TE bit is cleared to 0, the transmitter is initialized regardless of the current transmission

state, the TxD pin becomes an I/O port, and 0 is output from the TxD pin.

Receive Error Flags and Transmit Operations (Synchronous Mode Only):

Transmission cannot be started when a receive error flag (ORER, PER, or FER) is set to 1, even if

the TDRE flag is cleared to 0. Be sure to clear the receive error flags to 0 before starting

transmission.

Note also that receive error flags cannot be cleared to 0 even if the RE bit is cleared to 0.

Receive Data Sampling Timing and Reception Margin in Asynchronous Mode:

In asynchronous mode, the SCI operates on a base clock with a frequency of 16 times the transfer

rate.

In reception, the SCI samples the falling edge of the start bit using the base clock, and performs

internal synchronization. Receive data is latched internally at the rising edge of the 8th pulse of the

base clock. This is illustrated in figure 15.23.

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