PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
Word Bits
Parameter
Description
22:21 ifsm_state
IMA Frame Synchronization Mechanism State.
This state is maintained by the RDAT to indicate
the current state in the IFSM for this link.
00
IMA Hunt. Performs a cell-by-cell search
for IMA framing. Cells are not written to the DCB.
01
IMA PreSync. Performs a frame-by-frame
search for valid ICP cells. Cells are not written to
the DCB (although write pointers are maintained).
10
IMA Sync. Verifies IMA framing on a
frame-by-frame basis. Valid cells are written to
the DCB.
11
Reserved.
20:18 state_cnt
State count. This count is used within the IFSM,
and has dual meaning, depending on the state.
In the IMA PreSync state, this is the current
number of consecutive valid ICP cells. This value
is compared against the device gamma value to
determine when the IFSM may enter the IMA
Sync state from the IMA PreSync state. Once the
IMA Sync or Hunt state is entered, this value is
reset to 0.
In the IMA Sync state, this is the current number
of consecutive errored ICP cells. This value is
compared against the device beta value to
determine when the IFSM may enter the IMA Hunt
state from the IMA Sync state. Once the IMA
Hunt state is entered, or a non-errored cell is
received, this value is reset to 0.
17:16 invalid_cnt
Current number of consecutive invalid ICP cells.
This value is compared against the device alpha
value to determine when the IFSM may enter the
IMA Hunt state from the IMA Sync state. Once
the IMA Hunt state is entered, or a valid cell is
received, this value is reset to 0, and this value
may only be incremented in the IMA Sync state.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
228
PMC [ PMC-SIERRA, INC ]
