
Chapter 13 Serial Communications Interface (S12SCIV2) Block Description
402
MC9S12C-Family / MC9S12GC-Family
Freescale Semiconductor
Rev 01.24
If start bit verication 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 13-12 summarizes the results of the data bit samples.
NOTE
The RT8, RT9, and RT10 samples do not affect start bit verication. If any
or all of the RT8, RT9, and RT10 start bit samples are logic 1s following a
successful start bit verication, the noise ag (NF) is set and the receiver
assumes that the bit is a start bit (logic 0).
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10.
Table 13-13summarizes the results of the stop bit samples.
Table 13-13. Stop Bit Recovery
100
Yes
1
101
No
0
110
No
0
111
No
0
Table 13-12. Data Bit Recovery
RT8, RT9, and RT10 Samples
Data Bit Determination
Noise Flag
000
0
001
0
1
010
0
1
011
1
100
0
1
101
1
110
1
111
1
0
RT8, RT9, and RT10 Samples
Framing Error Flag
Noise Flag
000
1
0
001
1
010
1
011
0
1
100
1
101
0
1
110
0
1
111
0
Table 13-11. Start Bit Verication
RT3, RT5, and RT7 Samples
Start Bit Verication
Noise Flag