VSC6134
Datasheet
Table 50. RXSTFD1 and RXSTFD0 Output Stuff Column Content
Cycle Number
1-128
Size
Description
16 bytes
42 bits
16 bytes
42 bits
16 bytes
42 bits
16 bytes
42 bits
OPU stuff bytes from row #1
Reserved (000...)
129-170
171-298
299-340
341-468
469-510
511-638
639-680
OPU stuff bytes from row #2
Reserved (000...)
OPU stuff bytes from row #3
Reserved (000...)
OPU stuff bytes from row #4
Reserved (000...)
2.9.5
Overhead Processing
2.9.5.1
MFAS Monitor
The MFAS monitor continuously monitors received MFAS bytes. Two consecutive OTUk frames with
an error-free MFAS sequence causes the MFAS monitor to enter the in-multiframe (IM) state. If the
received MFAS byte does not match the expected MFAS value for five consecutive OTUk frames, then
the MFAS monitor enters the out-of-multiframe (OOM) state. A live bit OTUk_OOML indicates
whether the MFAS monitor is currently in the IM state (OTUk_OOML = 0) or the OOM state
(OTUk_OOML = 1). Each change of the live bit sets the status bit OTUk_OOMS. The status bit and the
mask bit OTUk_OOMM create a maskable hardware interrupt.
If the MFAS monitor is persistently in the OOM state for a number of consecutive FEC frames, the
MFAS monitor enters a loss-of-multiframe (LOM) state and sets the live bit OTUk_LOML. Register
bits OTUk_LOMTHRSHLD[7:0] hold the value for the number of frames and its default value of 0xF6
is equal to about 3 ms. The MFAS monitor clears the LOM condition and sets the OTUk_LOML live bit
low when entering the IM state. Each change of the live bit sets the status bit OTUk_LOMS. The status
bit and the mask bit OTUk_LOMM create a maskable hardware interrupt.
When the MFAS monitor is in the IM state, an internal counter generates an expected MFAS count
which indexes all TTI, FTFL and PSI bytes in their respective stacks.
The condition [LOS or (OOF AND LOF)], if true, disables MFAS monitoring if the MFAS monitor is in
the out-of-multiframe state.
2.9.5.2
OTUk Section Monitor (SM)
SM TTI Monitor
The SM TTI monitor stores the SM TTI bytes in the stack OTUk_SM_TTI[31:0][15:0] at locations
pointed to by MFAS. The microprocessor can point to any byte in the stack by initializing the
microprocessor stack pointer OTUk_SM_TTIPNT[4:0]. Each microprocessor read of, or write to, the
stack automatically increments the microprocessor stack pointer. (Writes to the stack are for testing
purposes only.)
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VMDS-10185 Revision 4.0
July 2006
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
