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

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
Freescale Semiconductor
Enhanced Serial Communications Interface (ESCI) Module
Data Sheet
229