MC908AS60ACFU Datasheet, PDF (187/414 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Functional Description
To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7. Table
18-5 summarizes the results of the start bit verification samples.
Table 18-5. 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 18-6 summarizes the results of the data bit samples.
Table 18-6. 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.
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Freescale Semiconductor
187