Serial Communications Interface Module (SCI)
Functional Description
MC68HC908AB32
—
Rev. 1.0
Technical Data
MOTOROLA
Serial Communications Interface Module (SCI)
255
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
shows how much a slow received character 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.
Figure 15-7. Slow Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times
×
16 RT 10 RT cycles = 154 RT cycles.
With the misaligned character shown in
, the receiver counts
154 RT cycles at the point when the count of the transmitting device is
9 bit times
×
16 RT 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 10 RT cycles = 170 RT cycles.
MSB
STOP
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RT10
RT11
RT12
RT13
RT14
RT15
RT16
DATA
SAMPLES
RECEIVER
RT CLOCK
154
147
–
154
--------------------------
100
×
4.54%
=
Summary of Contents for MC68HC908AB32
Page 1: ...MC68HC908AB32 D REV 1 0 MC68HC908AB32 HCMOS Microcontroller Unit TECHNICAL DATA ...
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Page 68: ...FLASH Memory Technical Data MC68HC908AB32 Rev 1 0 68 FLASH Memory MOTOROLA ...
Page 84: ...EEPROM Technical Data MC68HC908AB32 Rev 1 0 84 EEPROM MOTOROLA ...
Page 390: ...Ordering Information Technical Data MC68HC908AB32 Rev 1 0 390 Ordering Information MOTOROLA ...
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