S/UNI-IMA-4 Telecom Standard Product Data Sheet
Released
Word Bits
Parameter
ifsm_state
Description
22:21
IMA Frame Synchronization Mechanism State. This state is
maintained by the RDAT to indicate the current state in the
IFSM for this link.
00
IMA Hunt. Performs a cell-by-cell search for IMA
framing. Cells are not written to the DCB.
01
IMA PreSync. Performs a frame-by-frame search
for valid ICP cells. Cells are not written to the DCB (although
write pointers are maintained).
10
IMA Sync. Verifies IMA framing on a frame-by-
frame basis. Valid cells are written to the DCB.
11 Reserved.
20:18
state_cnt
State count. This count is used within the IFSM, and has
dual meaning, depending on the state.
In the IMA PreSync state, this is the current number of
consecutive valid ICP cells. This value is compared against
the device gamma value to determine when the IFSM may
enter the IMA Sync state from the IMA PreSync state. Once
the IMA Sync or Hunt state is entered, this value is reset to 0.
In the IMA Sync state, this is the current number of
consecutive errored ICP cells. This value is compared
against the device beta value to determine when the IFSM
may enter the IMA Hunt state from the IMA Sync state.
Once the IMA Hunt state is entered, or a non-errored cell is
received, this value is reset to 0.
17:16
15:0
invalid_cnt
write_ptr
Current number of consecutive invalid ICP cells. This value is
compared against the device alpha value to determine when
the IFSM may enter the IMA Hunt state from the IMA Sync
state. Once the IMA Hunt state is entered, or a valid cell is
received, this value is reset to 0, and this value may only be
incremented in the IMA Sync state.
Current delay compensation buffer write pointer for this link.
The least significant portion of the write pointer is the cell
number within the IMA frame, while the most significant
portion represents the IMA Frame Sequence Number. The
actual number of bits per field depends on the value for M for
this link. Bits 9:0 for MAX_DCB_DEPTH = 1024 always
represent the actual buffer write pointer (or bits 7:0 for
MAX_DCB_DEPTH = 256).
The write pointer is initialized by the RDAT when a valid ICP
cell is received while in the IMA Hunt state, and is
incremented otherwise. Only bits 12:0 are used for overrun
detection, underrun detection, and differential delay
calculations. The most significant 3 bits are only used for
IFSN validation.
Each increment of the write pointer represents a single cell
time at the link line rate. All write pointers within a group can
be compared in order to determine the differential delay.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2020889, Issue 2
222
PMC [ PMC-SIERRA, INC ]
