PM7346 datasheet(83/419 Pages) PMC

83 / 419 page

PM7346 S/UNI-QJET

DATASHEET

PMC-960835

ISSUE 6

SATURN QUAD USER NETWORK INTERFACE FOR J2, E3, T3

PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND ITS CUSTOMERS’ INTERNAL USE 62

m-bits, and Remote Loss of Frame (a-bit) are detected by the J2-FRMR. In

addition to providing indication signals of these states, the J2-FRMR will

optionally generate an interrupt when any of these status signals changes.

J2 LOS is declared when no marks have been received for one of 15, 31, 63, or

255 consecutive bit periods. J2 LOS is cleared when either 15, 31, 63, or 255

consecutive bit periods have passed without an excessive zeros (8 or more

consecutive zeros) detection as required by ITU-T G.775.

J2 LOF is declared when 7 or more consecutive multiframes with errored framing

patterns are received. The J2 LOF is cleared when 3 or more consecutive

multiframes with correct framing patterns are received. A framing algorithm

which takes into account the CRC calculation is also available. The framing

algorithms are described in the following text.

J2 Physical Layer AIS is declared when 2 or less zeros are detected in a

sequence of 3156 bits. It is cleared when 3 or more zeros is detected in a

sequence of 3156 bits as required by ITU-T G.775.

J2 Payload AIS is detected when the incoming J2 payload has 2 or less zeros in

a sequence of 3072 bits. It is cleared when 3 or more zeros are detected in a

sequence of 3072 bits.

The J2-FRMR may be forced to re-frame by microprocessor control. Similarly,

the microprocessor may disable the J2-FRMR from reframing due to framing bit

errors.

The J2-FRMR may be configured, and all sources of interrupts may be masked

or acknowledged, via internal registers. These internal registers are accessed

via a generic microprocessor bus.

9.3.1 J2 Frame Find Algorithms

The J2-FRMR searches for frame alignment using one of two algorithms, as

selected by the CRC_REFR bit in the J2-FRMR Configuration Register.

When the CRC_REFR bit is set to logic 0, the J2-FRMR uses only the frame

alignment sequence to find frame, searching for three consecutive correct frame

alignment sequences. The frame find block searches for the entire 9-bit

sequence (spread over two multiframes) at the same time, greatly reducing the

time required to find frame alignment. The framing process with CRC-REFR

cleared is illustrated in Figure 8.

PM7346 Datasheet(PDF) 83 Page - PMC-Sierra, Inc