PM7345 datasheet(55/306 Pages) PMC

55 / 306 page

PM7345 S/UNI-PDH

DATA SHEET

PMC-931011

ISSUE 6

SATURN USER-NETWORK INTERFACE

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

FUNCTIONAL DESCRIPTION

9.1

DS3 Framer

The DS3 Framer (T3-FRMR) Block integrates circuitry required for decoding a

B3ZS-encoded signal and framing to the resulting DS3 bit stream. The T3-FRMR is

directly compatible with the M23 and C-bit parity DS3 applications.

The T3-FRMR decodes a B3ZS-encoded signal and provides indications of line

code violations. The B3ZS decoding algorithm and the LCV definition can be

independently chosen through software. A loss of signal (LOS) defect is also

detected for B3ZS encoded streams. LOS is declared when inputs RPOS and

RNEG contain zeros for 175 consecutive RCLK cycles. LOS is removed when the

ones density on RPOS and/or RNEG is greater than 33% for 175 ±1 RCLK cycles.

The framing algorithm examines five F-bit candidates simultaneously. When at least

one discrepancy has occurred in each candidate, the algorithm examines the next

set of five 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, and M3 are following the 010 pattern). Framing is declared, and out-

of-frame is removed, 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 1.5 ms.

While the T3-FRMR is synchronized to the DS3 M-frame, the F-bit and M-bit

positions in the DS3 stream are examined. An out-of-frame defect is detected when

3 F-bit errors out of 8 or 16 consecutive F-bits are observed (as selected by the

M3O8 bit in the DS3 FRMR Configuration Register), 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 by 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 high bit error rate, than the 3 out of 16 consecutive F-bits ratio.

Either out-of-frame criteria allows an out-of-frame defect to be detected quickly

when the M-subframe alignment patterns or, optionally, when the M-frame alignment

pattern is lost.

Also while in-frame, line code violations, 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, are accumulated over 1 second

intervals with the Performance Monitor (PMON). Note that the framer is an off-line

PM7345 Datasheet(PDF) 55 Page - PMC-Sierra, Inc

PM7345 Datasheet(HTML) 55 Page - PMC-Sierra, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL