MC68HC908MR8 Datasheet, PDF (259/372 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface (SCI)
Functional Description
To determine the value of a data bit and to detect noise, recovery logic
takes samples at RT8, RT9, and RT10. Table 13-2 summarizes the
results of the data bit samples.
Table 13-2. 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 13-3 summarizes the results of the stop bit
samples.
Table 13-3. 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
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Serial Communications Interface (SCI)
Technical Data
259