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XRT94L33
xr
Rev.1.2.0.
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
382
SF CLEARANCE CRITERIA – PER THE “BURST” SF DETECTOR
In this case, the user specifies two parameters to define the SF Clearance criteria.
The maximum number of B2 errors (e.g., a B2 error-threshold) accumulated over a given “SF Clear
Interval” time period.
The length (in terms of SONET frame periods) of this “SF Clear Interval” time period.
Once the user defines these parameters, then the Receive STS-3 TOH Processor block will begin to count
the cumulative number of B2 errors that it detects within a “sliding window” of time. The length of this “sliding
window of time” is dictated by the user-defined “SF Clear Interval” time period.
If the Receive STS-3 TOH Processor block is currently declaring the SF condition, and if it continues to detect
more than the “B2 error threshold” number of B2 errors; within the “SF Clear Interval” of time, then it will NOT
clear the SF condition. Conversely, if the Receive STS-3 TOH Processor block detects less than the “B2
error threshold” number of B2 errors, within the “SF Clear Interval” of time, then it will clear the SF condition.
SPECIFYING THE “B2 ERROR THRESHOLD” FOR CLEARING SF – THE SF “BURST” DETECTOR
The user can specify the “B2 Error Threshold” by writing the appropriate value into the “Receive STS-3
Transport – Receive SF Burst Error Tolerance – Byte 1 and Byte 0” registers, as depicted below.
Receive STS-3 Transport – Receive SF Burst Error Tolerance – Byte 1 (Address = 0x1156)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
SF_BURST_TOLERANCE[15:8]
R/W
1
Receive STS-3 Transport – Receive SF Burst Error Tolerance – Byte 0 (Address = 0x1157)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
SF_BURST_TOLERANCE[7:0]
R/W
1
Notes:
The “Receive STS-3 Transport- Receive SF Burst Error Tolerance – Byte 1 and Byte 0” registers permit the user to write
in a 16-bit expression for the “B2 Error Threshold”.
The “default” value for the “B2 Error Threshold” is “0xFFFF”.
The “Receive STS-3 Transport – Receive SF Burst Error Tolerance” registers are used to set both the “SF Declaration”
and “SF Clearance” criteria. Therefore, any value that the user writes into this register (to set the “SF Clearance”
criteria – per the “SF Burst” Detector) will also effect the “SF Declaration” criteria (per the “SF Burst” Detector).