MC908AB32CFUE Datasheet, PDF (253/392 Pages) Freescale Semiconductor, Inc – Microcontrollers

Serial Communications Interface Module (SCI)
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 15-2 summarizes the results of
the start bit verification samples.
Table 15-2. 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
Start bit verification is not successful if any two of the three verification
samples are logic 1s. 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 15-3 summarizes the
results of the data bit samples.
Table 15-3. 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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Serial Communications Interface Module (SCI)
Technical Data
253