AT24RF08C View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'AT24RF08C' PDF : 21 Pages View PDF
AT24RF08C
Reception: Decoding and Demodulation
For data received by the chip, a drop in amplitude is
interpreted as a low state, while an increase in amplitude
indicates a high state. The output of this demodulator is
inverted and then decoded using Manchester decoding
before being interpreted as commands or data.
In Manchester decoding, (sometimes called BiPhase),
there is a transition in the middle of each bit time. If this is a
high-to-low, the data state is a 0, and if low-to-high a 1.
Data is received by the chip at a rate of one bit (out of the
decoder) for each 64 carrier cycles.
Each command must be preceded by a command initiation
pattern (CIP). The receiver uses the leading edge of the
first modulation change of the CIP to automatically
synchronize to the incoming data stream. That edge must
occur during the tCMD1 interval after the end of the last bit
previously transmitted or received by the chip. This edge is
used to start a bit clock against which all remaining edges
are timed.
The remaining two edges within the CIP occur during the
middle of the first and third bit times of the command. They
must occur within specific time intervals (tCMD2) from the
beginning of the bit time, and their specific time locations
(within the bit times) are used to synchronize with
subsequent edges (tCMD3) occurring in the same direction
(rising or falling). Edges that correspond to Manchester
changes at the beginning/end of a bit are not explicitly used
by the chip.
If no edges of the CIP fall within the tCMD1 window after a
read of some sort (including ID read), the chip will
retransmit the data that was previously read.
The following diagram shows functional waveforms for data
reception.
Data Reception
13
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