HD64F3664BPV Datasheet, PDF (261/446 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 14 Serial Communication Interface 3 (SCI3)
14.8.2 Mark State and Break Sending
When TE is 0, the TxD pin is used as an I/O port whose direction (input or output) and level are
determined by PCR and PDR. This can be used to set the TxD pin to mark state (high level) or
send a break during serial data transmission. To maintain the communication line at mark state
until TE is set to 1, set both PCR and PDR to 1. As TE is cleared to 0 at this point, the TxD pin
becomes an I/O port, and 1 is output from the TxD pin. To send a break during serial transmission,
first set PCR to 1 and PDR to 0, and then clear TE to 0. When TE 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.
14.8.3 Receive Error Flags and Transmit Operations (Clocked Synchronous Mode Only)
Transmission cannot be started when a receive error flag (OER, 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.
14.8.4 Receive Data Sampling Timing and Reception Margin in Asynchronous Mode
In asynchronous mode, the SCI3 operates on a basic clock with a frequency of 16 times the
transfer rate. In reception, the SCI3 samples the falling edge of the start bit using the basic clock,
and performs internal synchronization. Receive data is latched internally at the rising edge of the
8th pulse of the basic clock as shown in figure 14.19.
Thus, the reception margin in asynchronous mode is given by formula (1) below.

M = _(0.5 –

1 _)–
2N
D – 0.5
N
– (L – 0.5) F
× 100(%)
Where
N: Ratio of bit rate to clock (N = 16)
D: Clock duty (D = 0.5 to 1.0)
L: Frame length (L = 9 to 12)
F: Absolute value of clock rate deviation
... Formula (1)
Rev. 6.00 Mar. 24, 2006 Page 231 of 412
REJ09B0142-0600