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Table 38-5. Data bit recovery (continued)
RT8, RT9, and RT10 samples
Data bit determination
Noise flag
100
0
1
101
1
1
110
1
1
111
1
0
Note
The RT8, RT9, and RT10 samples do not affect start bit
verification. If any or all of the RT8, RT9, and RT10 start bit
samples are logic 1s following a successful start bit verification,
the noise flag (S1[NF]) is set and the receiver assumes that the
bit is a start bit (logic 0). With the exception of when
C7816[ISO_7816E] is set/enabled, where the values of RT8,
RT9 and RT10 exclusively determine if a start bit exists.
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. The following table summarizes the results of the stop bit samples. In the event
that C7816[ISO_7816E] is set/enabled and C7816[TTYPE] = 0, verification of a stop bit
does not take place. Rather, starting with RT8 the receiver transmits a NACK as
programmed until time RT9 of the following time period. Framing Error detection is not
supported when C7816[ISO_7816E] is set/enabled.
Table 38-6. Stop bit recovery
RT8, RT9, and RT10 samples
Framing error flag
Noise flag
000
1
0
001
1
1
010
1
1
011
0
1
100
1
1
101
0
1
110
0
1
111
0
0
In the following figure, the verification samples RT3 and RT5 determine that the first low
detected was noise and not the beginning of a start bit. In this example
C7816[ISO_7816E] = 0. The RT clock is reset and the start bit search begins again. The
noise flag is not set because the noise occurred before the start bit was found.
Functional description
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
716
Freescale Semiconductor, Inc.