PM7367 datasheet(45/323 Pages) PMC

45 / 323 page

PM7367 FREEDM-32P32

DATA SHEET

PMC-1991499

ISSUE 2

FRAME ENGINE AND DATA LINK MANAGER

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

Figure 2 – CRC Generator

Dn-1

Message

Parity Check Digits

gn-1

LSB

MSB

8.2 Receive Channel Assigner

The Receive Channel Assigner block (RCAS) processes up to 32 serial links.

Each link is independent and has its own associated clock. For each link, the

RCAS performs a serial to parallel conversion to form data bytes. The data

bytes are multiplexed, in byte serial format, for delivery to the Receive HDLC

Processor / Partial Packet Buffer block (RHDL) at SYSCLK rate. In the event

where multiple streams have accumulated a byte of data, multiplexing is

performed on a fixed priority basis with link #0 having the highest priority and link

#31 the lowest.

Links containing a T1 or an E1 stream may be channelised. Data at each time-

slot may be independently assigned to a different channel. The RCAS performs

a table lookup to associate the link and time-slot identity with a channel. T1 and

E1 framing bits/bytes are identified by observing the gap in the link clock which is

squelched during the framing bits/bytes. For unchannelised links, clock rates are

limited to 52 MHz on link #0 to #2 and limited to 10 MHz for the remaining links.

All data on each link belongs to one channel. For the case of two unchannelised

links, the maximum link rate is 45 MHz for SYSCLK at 25 MHz and 52 MHz for

SYSCLK at 33 MHz. For the case of more numerous unchannelised links or a

mixture of channelise with unchannelised links, the total instantaneous link rate

over all the links is limited to 64 MHz. The RCAS performs a table lookup using

only the link number to determine the associated channel, as time-slots are

non-existent in unchannelised links.

The RCAS provides diagnostic loopback that is selectable on a per channel

basis. When a channel is in diagnostic loopback, stream data on the received

links originally destined for that channel is ignored. Transmit data of that channel

is substituted in its place.

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