PM7340-PI datasheet(86/334 Pages) PMC

86 / 334 page

PRELIMINARY

INVERSE MULTIPLEXING OVER ATM

PM7340 S/UNI-IMA-8

DATA SHEET

PMC-2001723

ISSUE 3

INVERSE MULTIPLEXING OVER ATM

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

IMA links. Idle cells will be treated as user cells by the RDAT for IMA processing

and will not be dropped at the IMA sub-layer.

10.2.4.4

DCB Playout

The IDCC scheduler provides the rate for data to be played out to the ATM layer

for an IMA group. For each cell to be played out, the IDCC generates a service

request. Upon the IDCC service request, the RDAT plays out data from the

FIFOs in a round-robin fashion. For each service request, the RDAT runs the

round robin servicing until it processes either a filler cell or user cell. If ICP cells

are encountered, the ICP cell is dropped and the servicing continues until a user

or filler cell is found. If a user cell is found, it is transferred from the external

memory to the appropriate group FIFO. If a filler cell is found, it is dropped.

The RDAT is not sensitive to the alignment of ICP cells within a group. There is

no performance degradation even if all of the ICP cells in a group have the same

offset.

If the device is in Any-PHY mode or UTOPIA L2 Single Port mode, there is only a

single FIFO shared among all of the groups. The RDAT ensures that no more

than 16 cells are stored in the shared FIFO for a single group. If the S/UNI-IMA-8

is in UTOPIA L2 Multi-port mode, each group has it’s own FIFO.

If the group FIFO is not emptied in a timely fashion, data is dropped; this is

similar to the procedure used by any other PHY level device. The IDCC service

request FIFO will always be serviced regardless of the state of the Group FIFO.

For multi-port mode, if the respective Group FIFO is full, the cell will be dropped.

In Any-PHY mode and UTOPIA L2 Single Port mode, if either the shared FIFO is

full or there are already 16 cells for the current group in the FIFO, the cell will be

dropped.

10.2.5 Link/Group State Machines

The Receive IMA Protocol Processor (RIPP) block is responsible for maintaining

and controlling the link and group state machines. The RIPP can accept

commands from the management plane to initiate group and link state machine

actions. The RIPP then controls the contents of ICP cells generated for the

transmit data path, as well as analyzes the link and group states received within

the ICP cells. The receive link and group states are utilized to maintain and

update the link and group states. The RIPP coordinates group wide state

transactions and performs the group wide procedures such as the Synchronized

Link activation during Group Start-up Procedure and the Link Addition and Slow

PM7340-PI Datasheet(PDF) 86 Page - PMC-Sierra, Inc

PM7340-PI Datasheet(HTML) 86 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