PM7340 S/UNI-IMA-8
PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
DATA SHEET
PMC-2001723
ISSUE 3
INVERSE MULTIPLEXING OVER ATM
the RDAT will always accept immediate notification of a stuff event, to support the
case when the 001 stuff cell was errored).
Figure 11
- Stuff Event with Errored ICP (Advanced Indication)
Time
M-1 Filler or
ATM Layer Cells
Stuff event
ICP Cell
ICP Cell
IFSN # i+3
LSI = 000
ICP Cell
IFSN # i+4
LSI = 111
ICP Cell
IFSN # i+2
LSI = 001
ICP Cell
Errored
ICP Cell
IFSN # i
IFSN # i+3
LSI = 000
LSI = 011
stuff_cnt =7
stuff_cnt =0
stuff_cnt =1
stuff_cnt =2
stuff_cnt =3
IFSN: IMA Frame Sequence Number
LSI: Link Stuffing Indication
Figure 12
- Invalid Stuff Sequence (Advanced Indication)
Time
M-1 Filler or
ATM Layer Cells
Stuff event
ICP Cell
IFSN # i+3
LSI = 000
ICP Cell
IFSN # i+3
LSI = 000
ICP Cell
IFSN # i+4
LSI = 111
ICP Cell
IFSN # i+2
LSI = 001
ICP Cell
IFSN #i+1
LSI=001
ICP Cell
IFSN # i
LSI = 011
stuff_cnt =7
stuff_cnt =0
stuff_cnt =1
stuff_cnt =2
stuff_cnt =3
IFSN: IMA Frame Sequence Number
LSI: Link Stuffing Indication
10.2.4.1.3
IMA Frame Synchronization with Stuff Events
The RDAT will maintain synchronization while receiving stuff events subjected to
HEC or CRC errors, as shown in Figure 13. When one of the ICP cells
comprising a stuff event is errored or invalid, the other will be used. If both are
errored or invalid, then the internally maintained stuff count will be used to
identify the stuff event (given that the advanced indicators were correct).
All of the cases assume that the IFSM is in the IMA Sync state prior to the
window shown, and that the current errored/invalid counts are zero. Cases (1)
through (6) require that alpha or beta be programmed to a value greater than one
for synchronization to be maintained. Case (7) requires that alpha or beta be
programmed to a value greater than two for synchronization to be maintained.
Case (7) also requires that advance link stuff indication be given prior to the
window shown in order to detect the stuff event.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
60
PMC [ PMC-SIERRA, INC ]
