HD6473032F16 Datasheet, PDF (520/847 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

Section 13 Serial Communication Interface
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 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 13.21.
16 clocks
Internal
base clock
8 clocks
0
7
15 0
7
15 0
Receive data
(RxD)
Start bit
D₀
D₁
Synchronization
sampling timing
Data sampling
timing
Figure 13.21 Receive Data Sampling Timing in Asynchronous Mode
Rev. 3.00 Mar 21, 2006 page 490 of 814
REJ09B0302-0300