MPC8280 datasheet(1212/1386 Pages) FREESCALE

1212 / 1386 page

Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

34-66

Freescale Semiconductor

4. GDS (Group Delay Synchronized)—Group delay synchronized achieved or group delay

synchronized not achieved. In some cases, it is not possible for the GDS to complete. GDS can not

complete if a link experiences problems during the GDS process - for example losing SYNC state

for the IFSM. If this occurs, it is not possible to determine the links true differential delay with

respect to other member links of the group. In order to determine if the GDS process completed

successfully, the ucode will set IGRSTATE[GDSS] to either of the following values after the GDS

interrupt has been generated:

— IGRSTATE[GDSS] = 00 - GDS process failed, a link lost IFSM SYNC during GDS process

— IGRSTATE[GDSS] = 11 - GDS process completed

Software can then read IGRSTATE[GDSS] and use this status information before deciding whether

to change the links to the active state or to try and resynchronize again at the group level. In

addition to the above status information, the ILRSTATE[ADD_NEW_M] bit of the link that caused

the failure of the GDS process will be flipped such that it is logically inverted with respect to the

ILRCNTL[ADD_NEW] bit. It is recommended however, that software, after GDS failure and

when restarting the GDS process, changes all of the links in the group to the group unassigned state

and then update the link and group parameters to their default values before starting the GDS

process again. Note that a link losing SYNC during the GDS process can cause DCBO interrupt

for other links in the group. If this situation occurs, the GDS process should be restarted as

described above.

5. IFSD (Link (IMA) Frame Synchronization Defect)—Indicates that the link has lost

synchronization (e.g., unexpected IFSN value for a number (GAMMA + 2) of consecutive frames).

If this condition persists, the link should be removed. The threshold that would trigger the removal

of the link is system specific. The IFSD event corresponds to the “Loss of IMA Frame” (LIF) state

and the software should react to this by informing the FE (via the ICP cell, RxDefect = LIF) of the

problem. If the condition persists, IFSD events will continue to be generated every GAMMA+2

frames. The MPC8280 maintains counters (if enabled) to track the overall “quality” of a particular

link: see OIF (Out of IMA Frame) and ICPVIOL (ICP Violation) in Section 34.4.5.3, “IMA Link

Receive Statistics Table.” If the link returns to working state, the MPC8280 will automatically

perform Link Delay Synchronization and generate an LDS event upon achieving synchronization.

The software can use one of the MPC8280 timers as a time stamp when handling IFSD events and

check if the “persistence” time threshold has been crossed when subsequent events take place. The

LIF state time stamp should be reset when the IFSW event is reported.

6. IFSW (Link (IMA) Frame Synchronization Working)—Indicates that the link is has achieved

frame synchronization. This event is reported when a link has been assigned to a group (start-up or

link addition) or it was previously assigned and working, but had a defect (see IFSD event). If

going from defect to working, the software should update the RxDefect field of the ICP. Again, a

time stamp (timer) can be used to measure the “persistence” time.

7. DSL (DCB Synchronization Lost)—Indicates that a link in a group with IGRSTATE[GDSS] = 11

loses synchronization and enters the HUNT state at the IFSM. When this interrupt occurs, the link

should be removed by software, and the CPM will no longer perform the automatic LASR

procedure. Note that when the interrupt is generated, the ILRSTATE[DL] bit is set, and the

software should clear the IMA group and link receive state information as described above for the

GDS interrupt.

MPC8280 Datasheet(PDF) 1212 Page - Freescale Semiconductor, Inc

MPC8280 Datasheet(HTML) 1212 Page - Freescale Semiconductor, 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