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MC9S12P32CFT Datasheet, PDF (388/566 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers | |||
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Serial Communication Interface (S12SCIV5)
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. Table 11-18 summarizes the results of the data bit samples.
Table 11-18. Data Bit Recovery
RT8, RT9, and RT10 Samples
000
001
010
011
100
101
110
111
Data Bit Determination
0
0
0
1
0
1
1
1
Noise Flag
0
1
1
1
1
1
1
0
NOTE
The RT8, RT9, and RT10 samples do not affect start bit veriï¬cation. If any
or all of the RT8, RT9, and RT10 start bit samples are logic 1s following a
successful start bit veriï¬cation, the noise ï¬ag (NF) is set and the receiver
assumes that the bit is a start bit (logic 0).
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 11-19
summarizes the results of the stop bit samples.
Table 11-19. Stop Bit Recovery
RT8, RT9, and RT10 Samples
000
001
010
011
100
101
110
111
Framing Error Flag
1
1
1
0
1
0
0
0
Noise Flag
0
1
1
1
1
1
1
0
In Figure 11-22 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.
S12P-Family Reference Manual, Rev. 1.13
388
Freescale Semiconductor
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