MC68HC812A4 Datasheet, PDF (242/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include

Serial Communications Interface Module (SCI)
Figure 14-11 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.
In Figure 14-12 a noise burst makes the majority of data samples RT8,
RT9, and RT10 high. This sets the noise flag but does not reset the RT
clock. In start bits only, the RT8, RT9, and RT10 data samples are
ignored.
START BIT
LSB
RXD
NO START BIT FOUND
SAMPLES 1 1 1 1 1 1 1 1 1 0
0
1
100000000
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
Figure 14-11. Start Bit Search Example 5
START BIT
LSB
RXD
SAMPLES 1 1 1 1 1 1 1 1 1 0
0
0
0101
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
Figure 14-12. Start Bit Search Example 6
MC68HC812A4 — Rev. 3.0
242
Serial Communications Interface Module (SCI)
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