PM7341 datasheet(89/413 Pages) PMC

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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

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

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