S/UNI-IMA-4 Telecom Standard Product Data Sheet
Released
13.5.11 Deleting a Link from a Group
A link can be deleted from a group by using the delete Link command. On the transmit side, the
link will stop accepting ATM cells immediately and will transmit filler cells only. The links
will be removed from the TX round robin on the next frame boundary. On the receive side, the
deleted link/links will transition to the Deleted state to ensure that all transmitted data is
received into the DCB buffer. Once the FE TX state is detected as not active or the
RX_LINK_DELETED timeout occurs, the RX links stop writing data to the DCB buffers. The
DCB buffers allowed to underrun (preserving any previously stored data) prior to being disabled
and removed from the receive round robin. The RX_LINK_EN bits and TX_LINK_EN bits in
the RIPP Link context records should be monitored to determine when the links can be
reassigned to a different group.
13.5.12 Test Pattern Procedures
The test pattern procedure consists of 2 parts, issuing the test pattern and checking the test
pattern.
To issue a test pattern, the Update_test_ptn command is used. This starts the transmission of the
new test pattern. PM must take care to wait at least 2 frames in between updates to the test
pattern in order to comply with the IMA test pattern standard. The S/UNI-IMA-4 will always
loopback the test pattern indicated in the ICP cell.
Since each link may experience different round trip delays, the checking of the test pattern is
split between the user and the S/UNI-IMA-4. The S/UNI-IMA-4 will compare test pattern
received in the ICP cell with the test pattern that was sent on every received ICP cell. The
S/UNI-IMA-4 stores the success or failure of this operation in the word 9 of the RIPP Group
Context register. The user is responsible for checking the results after a sufficient time has
passed for a round trip delay on all links.
13.5.13 Removing Accumulated Delay from a Group
In certain situations, such as when the RX_ADD_DELAY_EN is enabled, a group may
accumulate delay over time (after multiple LASR operations). A group may also accumulate
delay due to many changes of far end transmit TRL LID (due to slight rate inaccuracies that
accumulate when switching references). It may also be desirable to remove delay if a link is
rejected from a LASR operation with a DIFF_DELAY_INT (and rx_add_delay_en is disabled
for the group). In order to remove unwanted delay, the adjust_delay command can be issued. A
read_delay command may be issued to determine the smallest amount of delay in the group
(associated with the link with the longest transport delay). The maximum amount of delay that
may be removed from the group without causing LODS on links in the group is:
Actual delay (A) = Min(group depths) – Min_lower_guardband
The Min_lower_guardband is specified in register 0x208, and defaults to a value of 3. Due to
internal deration of the scheduling rate associated with ICP cells, the device will derate the
requested delay specified (R) with the command:
A = R * (M/(M-1)), where M is the frame length (32, 64, 128, 256)
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2020889, Issue 2
286
PMC [ PMC-SIERRA, INC ]
