Chapter 13 Serial Communications Interface (S12SCIV2) Block Description
404
MC9S12C-Family / MC9S12GC-Family
Freescale Semiconductor
Rev 01.24
In
, a large burst of noise is perceived as the beginning of a start bit, although the test sample
at RT5 is high. The RT5 sample sets the noise flag. Although this is a worst-case misalignment of perceived
bit time, the data samples RT8, RT9, and RT10 are within the bit time and data recovery is successful.
Figure 13-16. Start Bit Search Example 3
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 13-17. Start Bit Search Example 4
RESET RT CLOCK
RT1
RT1
RT1
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RT10
RT13
RT12
RT11
RT16
RT15
RT14
RT4
RT3
RT2
RT1
RT5
RT6
RT7
RT8
RT9
SAMPLES
RT CLOCK
RT CLOCK COUNT
ACTUAL START BIT
Rx input Signal
1
0
1
1
1
0
0
0
0
LSB
0
PERCEIVED START BIT
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
Rx Input Signal
1
1
1
1
1
0
0
1
LSB
1
1
1
1
Summary of Contents for MC9S12C Family
Page 689: ......