Datasheet

Functional Description
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Freescale Semiconductor 187
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.
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.
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.
Table 18-5. Start Bit Verification
RT3, RT5, and RT7 Samples Start Bit Verification Noise Flag
000 Yes 0
001 Yes 1
010 Yes 1
011 No 0
100 Yes 1
101 No 0
110 No 0
111 No 0
Table 18-6. Data Bit Recovery
RT8, RT9, and RT10 Samples Data Bit Determination Noise Flag
000 0 0
001 0 1
010 0 1
011 1 1
100 0 1
101 1 1
110 1 1
111 1 0