Slow Data Tolerance - NXP Semiconductors MC9S08SU16 Reference Manual

22.5.5.1 Slow data tolerance

Figure 22-4 shows how much a slow received frame can be misaligned without causing a
noise error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives
in time for the stop bit data samples at RT8, RT9, and RT10.
RECEIVER
RT CLOCK
For an 8-bit data and 1 stop bit character, data sampling of the stop bit takes the receiver
9 bit times x 16 RT cycles +10 RT cycles =154 RT cycles.
With the misaligned character shown in
the point when the count of the transmitting device is 9 bit times x 16 RT cycles + 3 RT
cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of
a slow 8-bit data and 1 stop bit character with no errors is:
((154 - 147) / 154) x 100 = 4.54%
For a 9-bit data or 2 stop bits character, data sampling of the stop bit takes the receiver 10
bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in
the point when the count of the transmitting device is 10 bit times x 16 RT cycles + 3 RT
cycles = 163 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of
a slow 9-bit or 2 stop bits character with no errors is:
((170 - 163) / 170) X 100 = 4.12%
For a 9-bit data and 2 stop bit character, data sampling of the stop bit takes the receiver
11 bit times x 16 RT cycles + 10 RT cycles = 186 RT cycles.
With the misaligned character shown in
the point when the count of the transmitting device is 11 bit times x 16 RT cycles + 3 RT
cycles = 179 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of
a slow 9-bit and 2 stop bits character with no errors is: ((186 - 179) / 186) X 100 = 3.76%
NXP Semiconductors
MSB
Figure 22-4. Slow data
Figure
Figure
Figure
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
Chapter 22 Serial Communications Interface (SCI)
STOP
DATA
SAMPLES
22-4, the receiver counts 154 RT cycles at
22-4, the receiver counts 170 RT cycles at
22-4, the receiver counts 186 RT cycles at
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