MC68HC908GZ8 Datasheet, PDF (229/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Enhanced Serial Communications Interface (ESCI) Module
Functional Description
To verify the start bit and to detect noise, data recovery logic takes samples at RT3,
RT5, and RT7. Table 19-2 summarizes the results of the start bit verification
samples.
Table 19-2. Start Bit Verification
RT3, RT5, and RT7 Samples
000
001
010
011
100
101
110
111
Start Bit Verification
Yes
Yes
Yes
No
Yes
No
No
No
Noise Flag
0
1
1
0
1
0
0
0
If start bit verification is not successful, the RT clock is reset and a new search for
a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic takes
samples at RT8, RT9, and RT10. Table 19-3 summarizes the results of the data
bit samples.
Table 19-3. Data Bit Recovery
RT8, RT9, and RT10 Samples
000
001
010
011
100
101
110
111
Data Bit Determination
0
0
0
1
0
1
1
1
Noise Flag
0
1
1
1
1
1
1
0
NOTE:
The RT8, RT9, and RT10 samples do not affect start bit verification. If any or all of
the RT8, RT9, and RT10 start bit samples are logic 1s following a successful start
bit verification, the noise flag (NF) is set and the receiver assumes that the bit is a
start bit.
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9,
and RT10. Table 19-4 summarizes the results of the stop bit samples.
MC68HC908GZ8
MOTOROLA
Enhanced Serial Communications Interface (ESCI) Module
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Data Sheet
229