Table 38-5. Data bit recovery (continued)RT8, RT9, and RT10 samples Data bit determination Noise flag100 0 1101 1 1110 1 1111 1 0NoteThe RT8, RT9, and RT10 samples do not affect start bitverification. If any or all of the RT8, RT9, and RT10 start bitsamples are logic 1s following a successful start bit verification,the noise flag (S1[NF]) is set and the receiver assumes that thebit is a start bit (logic 0). With the exception of whenC7816[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, andRT10. The following table summarizes the results of the stop bit samples. In the eventthat C7816[ISO_7816E] is set/enabled and C7816[TTYPE] = 0, verification of a stop bitdoes not take place. Rather, starting with RT8 the receiver transmits a NACK asprogrammed until time RT9 of the following time period. Framing Error detection is notsupported when C7816[ISO_7816E] is set/enabled.Table 38-6. Stop bit recoveryRT8, RT9, and RT10 samples Framing error flag Noise flag000 1 0001 1 1010 1 1011 0 1100 1 1101 0 1110 0 1111 0 0In the following figure, the verification samples RT3 and RT5 determine that the first lowdetected was noise and not the beginning of a start bit. In this exampleC7816[ISO_7816E] = 0. The RT clock is reset and the start bit search begins again. Thenoise flag is not set because the noise occurred before the start bit was found.Functional descriptionKL27 Sub-Family Reference Manual , Rev. 5, 01/2016716 Freescale Semiconductor, Inc.
