Datasheet

Infrared Serial Communications
Technical Data MC68HC908LJ12 — Rev. 2.1
242 Infrared Serial Communications Interface Module (IRSCI) Freescale Semiconductor
To locate the start bit, data recovery logic does an asynchronous search
for a logic 0 preceded by three logic 1s. When the falling edge of a
possible start bit occurs, the RT clock begins to count to 16.
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 13-2 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 13-3 summarizes the
results of the data bit samples.
Table 13-2. 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 13-3. 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