MC68908GZ8MFJE Datasheet, PDF (191/314 Pages) Freescale Semiconductor, Inc – Microcontrollers

Functional Description
Table 15-2. Start Bit Verification (Continued)
RT3, RT5, and RT7 Samples
011
100
101
110
111
Start Bit Verification
No
Yes
No
No
No
Noise Flag
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 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
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 15-4
summarizes the results of the stop bit samples.
Table 15-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples
000
001
010
011
100
101
110
111
Framing Error Flag
1
1
1
0
1
0
0
0
Noise Flag
0
1
1
1
1
1
1
0
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4
Freescale Semiconductor
191