s908gr32ag3vfa Freescale Semiconductor, Inc, s908gr32ag3vfa Datasheet - Page 162

• Manufacturer Part Number: s908gr32ag3vfa
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Enhanced Serial Communications Interface (ESCI) Module
actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing
error occurs. In most applications, the baud rate tolerance is much more than the degree of misalignment
that is likely to occur.
As the receiver samples an incoming character, it resynchronizes the RT clock on any valid falling edge
within the character. Resynchronization within characters corrects misalignments between transmitter bit
times and receiver bit times.
Slow Data Tolerance
Figure 13-8
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.
For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times × 16 RT cycles
+ 10 RT cycles = 154 RT cycles.
With the misaligned character shown in
the count of the transmitting device is 9 bit times × 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
character with no errors is:
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times × 16 RT cycles
+ 10 RT cycles = 170 RT cycles.
With the misaligned character shown in
the count of the transmitting device is 10 bit times × 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
character with no errors is:
Fast Data Tolerance
Figure 13-9
or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data
samples at RT8, RT9, and RT10.
162
shows how much a slow received character can be misaligned without causing a noise error
shows how much a fast received character can be misaligned without causing a noise error
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
RECEIVER
RT CLOCK
MSB
Figure
Figure
Figure 13-8. Slow Data
154 147
------------------------- -
170 163
------------------------- -
154
170
–
–
13-8, the receiver counts 154 RT cycles at the point when
13-8, the receiver counts 170 RT cycles at the point when
×
×
100
100
SAMPLES
=
=
DATA
4.54%
4.12%
STOP
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