PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
Device Address Pins: RADR(4:0) Channel Address Pins: RADR(4:0) Device Address Pins: RADR(4:0)
Select Pin: RENB
Select Pin: RENB
Select Pin: RENB
RX Transfer Cell Size: 8 bit X 53, 54, 55 or 56 Cell Size: 8 bit X 53 or 55 bytes
Cell Size: 8 bit X 54 or 56 bytes
bytes
Cell Size: 16 bit X 27, 28 or 29
words
Cell Size: 16 bit X 27 or 28 words Cell Size: 16 bit X 28 or 29 words
Enable Pin: RENB
Enable Pin: RENB
Enable Pin: RENB
Channel Address: Prepend or UDF Pause in Cell: w/ RENB
Channel Address: Prepend
10.1.4 ANY-PHY/UTOPIA Loopback
For diagnostic purposes, the capability to loopback all Any-PHY/UTOPIA traffic
back to the Any-PHY/UTOPIA bus is provided. Cells are taken from the Transmit
group FIFOs and placed into the respective Receive Group FIFOs, or to a single
FIFO on a space available basis.
10.2 IMA Sub-layer
10.2.1 Overview
The IMA protocol provides inverse multiplexing of a single ATM stream over
multiple physical links and reassembles the original cell stream at the far-end.
The inverse multiplexing is performed on a cell basis; hence, the IMA protocol is
described as a cell-based protocol. See Figure 9 below.
The protocol is based upon the concept of an IMA frame. An IMA frame is
programmable in size and is delineated by an IMA Control Protocol (ICP) Cell. It
is recommended that the ICP cells of each link in the IMA group be offset from
each other to reduce the notification time of link/group status changes.
The transmitter is responsible for aligning the IMA frames on all links within a
group, and for ensuring that cells are transmitted continuously by adding filler
cells as necessary. To maintain frame alignment in the presence of independently
timed line clocks, a cell based stuffing algorithm is utilized.
Since the IMA frames are aligned on transmission, this allows the receive end to
recover the IMA frames and align them to remove any differential delay between
the physical links.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
50
PMC [ PMC-SIERRA, INC ]
