Renesas SH7781 - Manual (Page 1127)

21. Serial Communication Interface with FIFO (SCIF)
Rev.1.00 Jan. 10, 2008 Page 1097 of 1658
REJ09B0261-0100
(4) Sending a Break Signal
The input/output condition and level of the SCIF_TXD pin are determined by bits SPB2IO and
SPB2DT in SCSPTR. This feature can be used to send a break signal.
After the serial transmitter is initialized and until the TE bit is set to 1 (enabling transmission), the
SCIF_TXD pin function is not selected and the value of the SPB2DT bit substitutes for the mark
state. The SPB2IO and SPB2DT bits should therefore be set to 1 (designating output and high
level) in the beginning.
To send a break signal during serial transmission, clear the SPB2DT bit to 0 (designating low
level), and then clear the TE bit to 0 (halting transmission). When the TE bit is cleared to 0, the
transmitter is initialized, regardless of the current transmission state, and 0 is output from the
SCIF_TXD pin.
(5) Receive Data Sampling Timing and Receive Margin in Asynchronous Mode
In asynchronous mode, the SCIF operates on a base clock with frequency of 16 times the bit rate.
In reception, the SCIF 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.
Figure 21.22 shows the timing.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5
16 clocks
8 clocks
-7.5 clocks
Start bit
+7.5 clocks
D0 D1
Receive data
(SCIF_RXD)
Synchronization
sampling
timing
Data sampling timing
Base clock
Figure 21.22 Receive Data Sampling Timing in Asynchronous Mode