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PM8313 View Datasheet(PDF) - PMC-Sierra

Part Name
Description
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PM8313
PMC-Sierra
PMC-Sierra PMC-Sierra
PM8313 Datasheet PDF : 192 Pages
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DATA SHEET
PMC-920702
ISSUE 5
PM8313 D3MX
M13 MULTIPLEXER
8 FUNCTIONAL DESCRIPTION
8.1 DS3 Framer
The DS3 Framer (FRMR) Block integrates circuitry required for decoding a
B3ZS-encoded signal and framing to the resulting DS3 bit stream. The FRMR is
directly compatible with the M23 and C-bit parity DS3 applications.
The FRMR decodes a B3ZS-encoded signal and provides indications of line
code violations. The B3ZS decoding algorithm and the LCV definition can
independently be chosen via software. Loss of signal is also detected.
The framing algorithm examines five F-bit candidates simultaneously. When at
least one discrepancy has occurred in all the candidates, the algorithm examines
the next set of candidates. When a single F-bit candidate remains in a set, the
first bit in the supposed M-subframe is examined for the M-frame alignment
signal (i.e. the M-bits, M1,M2,M3, are following the 010 pattern). Framing is
declared if the M-bits are correct for three consecutive M-frames while no
discrepancies have occurred in the F-bits. During the examination of the M-bits
the X-bits and P-bits are ignored. The algorithm gives a maximum average
reframe time of less than 1.5 ms.
Once in-frame, the FRMR provides indications of the M-frame and M-subframe
boundaries, and identifies the overhead bit positions in the incoming DS3 signal.
While the FRMR is in-frame, the F-bit and M-bit positions in the DS3 stream are
examined. Out-of-frame is declared when 3 F-bit errors out of 16 consecutive F-
bits or 8 consecutive F-bits are observed (selectable by the M3O8 bit), or when
one or more M-bit errors are detected in 3 out of 4 consecutive M-frames. The
M-bit error criteria for OOF can be disabled via the MBDIS bit in the DS3 Framer
configuration register. The 3 out of 8 consecutive F-bits out-of-frame ratio
provides more robust operation in the presence of a 10-3 bit error rate than the 3
out of 16 consecutive F-bits ratio (less than one false OOF every minute verses
one false OOF every 6 seconds, respectively); either choice of out-of-frame ratios
allows an out-of-frame to be declared quickly when the M-subframe alignment
patterns or, optionally, when the M-frame alignment is lost.
Also while in-frame, M-bit or F-bit framing bit errors and P-bit parity errors are
indicated. When C-bit parity mode is enabled, both C-bit parity errors and far
end block errors are indicated. These error indications, as well as the line code
violation and excessive zeros indication, may be accumulated over 1 second
intervals with the T3 Performance Monitor (PMON). Note that the framer is an
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