Datasheet

Serial Communications Interface (SCI)
MC9S12DP256 — Revision 1.1
Serial Communications Interface (SCI)
Figure 72 shows the effect of noise early in the start bit time. Although
this noise does not affect proper synchronization with the start bit time,
it does set the noise flag.
Figure 72 Start Bit Search Example 4
Figure 73 shows a burst of noise near the beginning of the start bit that
resets the RT clock. The sample after the reset is low but is not preceded
by three high samples that would qualify as a falling edge. Depending on
the timing of the start bit search and on the data, the frame may be
missed entirely or it may set the framing error flag.
Figure 73 Start Bit Search Example 5
RESET RT CLOCK
RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2 RT3 RT4 RT7 RT6 RT5
RT10
RT9 RT8
RT14 RT13 RT12 RT11 RT15 RT16
RT1 RT2 RT3
SAMPLES
RT CLOCK
RT CLOCK COUNT
PERCEIVED AND ACTUAL START BIT
sci_rx_ind
11111001
LSB
11 1 1
RESET RT CLOCK
RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2
RT3
RT4 RT7 RT6 RT5 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1
SAMPLES
RT CLOCK
RT CLOCK COUNT
START BIT
sci_rx_ind
11111010
LSB
11 1 1 1 0000000 0
NO START BIT FOUND
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc...