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PRELIMINARY
INVERSE MULTIPLEXING OVER ATM
PM7341 S/UNI-IMA-84
DATASHEET
PMC-2000223
ISSUE 4
INVERSE MULTIPLEXING OVER ATM
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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sequence of 111 followed by 000 is not considered an invalid stuff sequence (i.e.,
the RDAT will always accept immediate notification of a stuff event, to support the
case when the 001 stuff cell was errored).
Figure 12
- Stuff Event with Errored ICP (Advanced Indication)
IFSN: IMA Frame Sequence Number
LSI: Link Stuffing Indication
Time
M-1 Filler or
ATM Layer Cells
ICP Cell
IFSN # i+4
LSI = 111
Stuff event
ICP Cell
IFSN # i+3
LSI = 000
stuff_cnt =3
stuff_cnt =0
stuff_cnt =1
stuff_cnt =2
stuff_cnt =7
ICP Cell
IFSN # i+3
LSI = 000
ICP Cell
IFSN # i+2
LSI = 001
ICP Cell
Errored
ICP Cell
IFSN # i
LSI = 011
Figure 13
- Invalid Stuff Sequence (Advanced Indication)
IFSN: IMA Frame Sequence Number
LSI: Link Stuffing Indication
Time
M-1 Filler or
ATM Layer Cells
ICP Cell
IFSN # i+4
LSI = 111
Stuff event
ICP Cell
IFSN # i+3
LSI = 000
stuff_cnt =3
stuff_cnt =0
stuff_cnt =1
stuff_cnt =2
stuff_cnt =7
ICP Cell
IFSN # i+3
LSI = 000
ICP Cell
IFSN # i+2
LSI = 001
ICP Cell
IFSN #i+1
LSI=001
ICP Cell
IFSN # i
LSI = 011
10.2.4.4
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 14. 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