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MC9S12KG128 Datasheet, PDF (345/600 Pages) Freescale Semiconductor, Inc – Microcontrollers | |||
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Chapter 10 Serial Communications Interface (SCIV1)
In Figure 10-14 the veriï¬cation samples RT3 and RT5 determine that the ï¬rst low detected was noise and
not the beginning of a start bit. The RT clock is reset and the start bit search begins again. The noise ï¬ag
is not set because the noise occurred before the start bit was found.
START BIT
LSB
Rx Input Signal
SAMPLES 1 1 1 0
1
110
0
0
0000
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
Figure 10-14. Start Bit Search Example 1
In Figure 10-15, veriï¬cation sample at RT3 is high. The RT3 sample sets the noise ï¬ag. Although the
perceived bit time is misaligned, the data samples RT8, RT9, and RT10 are within the bit time and data
recovery is successful.
PERCEIVED START BIT
ACTUAL START BIT
LSB
Rx Input Signal
SAMPLES 1 1 1 1 1 0
1
0
0000
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
Figure 10-15. Start Bit Search Example 2
MC9S12KG128 Data Sheet, Rev. 1.15
Freescale Semiconductor
345
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