PM7347 datasheet(55/341 Pages) PMC

55 / 341 page

S/UNI®-JET Data Sheet

Released

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

Document ID: PMC-1990267, Issue 3

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 OOF defect is detected when three F-bit errors out of eight or 16

consecutive F-bits are observed (as selected by the M3O8 bit in the DS3 FRMR Configuration

frames. The M-bit error criteria for OOF can be disabled by the MBDIS bit in the DS3 Framer

Configuration Register. The three out of eight consecutive F-bits OOF ratio provides more robust

operation, in the presence of a high bit error rate, than the three out of 16 consecutive F-bits ratio.

Either OOF criteria allows an OOF 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, LCV, 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 FEBEs are indicated. These error

indications, as well as the LCV and excessive zeros indication, are accumulated over one second

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

indicating both OOF and COFA events. Even if an OOF is indicated, the framer will continue

indicating performance monitoring information based on the previous frame alignment.

Three DS3 maintenance signals (a RED alarm condition, the AIS, and the idle signal) are detected

by the T3-FRMR. The maintenance detection algorithm uses a simple integrator with a 1:1 slope

that is based on the occurrence of "valid" M-frame intervals. For the RED alarm, an M-frame is

said to be a "valid" interval if it contains a RED defect, defined as an occurrence of an OOF or

LOS event during that M-frame. For AIS and IDLE, an M-frame interval is "valid" if it contains

AIS or IDLE, defined as the occurrence of less than 15 discrepancies in the expected signal

pattern (1010.. for AIS, 1100.. for IDLE) while valid frame alignment is maintained. This

discrepancy threshold ensures the detection algorithms operate in the presence of a 10-3 bit error

rate. For AIS, the expected pattern may be selected to be: the framed "1010" signal; the framed

arbitrary DS3 signal and the C-bits all zero; the framed "1010" signal and the C-bits all zero; the

framed all-ones signal (with overhead bits ignored); or the unframed all-ones signal (with

overhead bits equal to ones).

Each "valid" M-frame causes an associated integration counter to increment; "invalid" M-frames

cause a decrement. With the "slow" detection option, RED, AIS, or IDLE are declared when the

respective counter saturates at 127, which results in a detection time of 13.5 ms. With the "fast"

detection option, RED, AIS, or IDLE are declared when the respective counter saturates at 21,

which results in a detection time of 2.23 ms, that is, 1.5 times the maximum average reframe

time. RED, AIS, or IDLE are removed when the respective counter decrements to zero. DS3 LOF

detection is provided as recommended by ITU-T G.783 with programmable integration periods of

1 ms, 2 ms, or 3 ms. While integrating up to assert LOF, the counter will integrate up when the

framer asserts an OOF condition and integrates down when the framer de-asserts the OOF

condition. Once an LOF is asserted, the framer must not assert OOF for the entire integration

period before LOF is de-asserted.

PM7347 Datasheet(PDF) 55 Page - PMC-Sierra, Inc