HD64F3039F18 Datasheet, PDF (410/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 11 Serial Communication Interface
Break Detection and Processing
Break signals can be detected by reading the RxD pin directly when a framing error (FER) is
detected. In the break state the input from the RxD pin consists of all 0s, so the FER flag is set and
the parity error flag (PER) may also be set. In the break state the SCI receiver continues to operate,
so if the FER flag is cleared to 0 it will be set to 1 again.
Sending a Break Signal
When the TE bit is cleared to 0 the TxD pin becomes an I/O port, the level and direction (input or
output) of which are determined by DR and DDR bits. This feature can be used to send a break
signal.
After the serial transmitter is initialized, the DR value substitutes for the mark state until the TE
bit is set to 1 (the TxD pin function is not selected until the TE bit is set to 1). The DDR and DR
bits should therefore both be set to 1 beforehand.
To send a break signal during serial transmission, clear the DR bit to 0, then clear the TE bit to 0.
When the TE bit is cleared to 0 the transmitter is initialized, regardless of its current state, so the
TxD pin becomes an input/output port outputting the value 0.
Receive Error Flags and Transmitter Operation (Synchronous Mode Only)
When a receive error flag (ORER, PER, or FER) is set to 1 the SCI will not start transmitting,
even if the TDRE flag is cleared to 0. Be sure to clear the receive error flags to 0 when starting to
transmit. Note that clearing the RE bit to 0 does not clear the receive error flags to 0.
Receive Data Sampling Timing in Asynchronous Mode and Receive Margin
In asynchronous mode the SCI operates on a base clock with 16 times the bit rate frequency. In
receiving, the SCI synchronizes internally with the fall of the start bit, which it samples on the
base clock. Receive data is latched at the rising edge of the eighth base clock pulse. See figure
11.21.
Rev.3.00 Mar. 26, 2007 Page 386 of 682
REJ09B0353-0300