Information

SAMPLES
Rx pin input
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
1 1 1
0 0
1
0 0 0 0
PERCEIVED START BIT
ACTUAL START BIT
LSB
RT1 RT1 RT1 RT1 RT2 RT4 RT3 RT5 RT6 RT7 RT8 RT9
RT10 RT11 RT15 RT14 RT13 RT12 RT16
RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9
Figure 48-162. Start bit search example 3 (C7816[ISO_7816E] = 0)
The following figure shows the effect of noise early in the start bit time. In this example
C7816[ISO_7816E] = 0. Although this noise does not affect proper synchronization with
the start bit time, it does set the noise flag.
SAMPLES
Rx pin input
RT CLOCK
RT CLOCK COUNT
RESET RT CLOCK
1 1 1 1
0
PERCEIVED AND ACTUAL START BIT
LSB
RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2 RT3
RT4
RT5
RT1 RT2 RT3
RT6 RT7 RT8 RT9
RT10 RT11 RT12 RT13 RT14 RT15 RT16
111 1 1 1
0
Figure 48-163. Start bit search example 4 (C7816[ISO_7816E] = 0)
The following figure shows a burst of noise near the beginning of the start bit that resets
the RT clock. In this example C7816[ISO_7816E] = 0. The sample after the reset is low
but is not preceded by three high samples that would qualify as a falling edge. Depending
on the timing of the start bit search and on the data, the frame may be missed entirely or it
may set the framing error flag.
Functional description
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
1346 Freescale Semiconductor, Inc.