CX28344 Conexant, CX28344 Datasheet - Page 92

• Manufacturer Part Number: CX28344
• Description: (CX2834x) Dual / Triple / Quad / Hex / Octal - Enhanced DS3 / E3 Framer
• Manufacturer: Conexant

Functional Description
2.2.5.4
2.2.5.5
2-46
Out of Frame (OOF)
In DS3 mode, an OOF event is declared, if in the receive data stream if there are three
or more F-bit framing bit errors in sixteen consecutive F-bits or one or more M-bit
FBEs per frame in two or more of four consecutive frames. The OOF is terminated
upon the non-occurrence of FBEs in three consecutive frames. The checking of F-bits
is done in batches of 16 F-bits and not as a sliding window.
In E3-G.751 mode, an OOF event is declared, if in the receive data stream, there is
one or more FBEs per frame in four consecutive frames. The OOF is terminated if
there are no FBEs in three consecutive frames.
In E3-G.832 mode, an OOF event is declared, if in the receive data stream, there is
one or more FBEs per frame in four consecutive frames. An OOF event is also
declared if there are PER in 986 or more frames in a block of 1000 frames. The OOF
is terminated if there are no FBEs in three consecutive frames.
The OOF event generates an OOFStrt interrupt indication and sets the OOF status
indication bit in the OOFAlm field of the Maintenance Status register. Terminating
the OOF event generates an OOFEnd Interrupt and clears the OOF status indication
bit.
In E3 mode, in the presence of OOF, RAI/RDI is transmitted on the transmit stream if
the AutoRAI field in the TransmitOverheadInsertion 1 Control register is set.
In both E3 and DS3 modes, in the presence of OOF, an all-1s sequence is transmitted
on the RXDAT toward the receive system side if the RxAutoAll1 field in Feature5
Control register is set.
Severely Errored Frame (SEF)
In DS3, an SEF event is declared when there are three or more F-bit FBEs in sixteen
consecutive F-bits. This is terminated when the framer is in frame (i.e., OOF end).
This is not specified in E3 mode.
The SEF event generates a SEFStrt interrupt indication. Since the termination criteria
for SEF is identical to OOF, there is no SEF-end interrupt indication.
NOTE:
NOTE:
Mindspeed Technologies™
While the framer is searching for a new framing template, the old one is maintained
for ongoing performance monitoring (e.g., FBE) and output signaling (e.g., RXMSY).
SEF detection employs a fixed-window algorithm. Two counters are maintained - one
for the number of F-bits encountered, and one for the number of errors encountered.
When an F-bit is encountered (once every 170 bits in the DS3 data stream) it is
checked to see if it has the value specified in the DS3 standard for its position in the
DS3 frame. If not, the error counter is incremented, and if it reaches a value of 3, SEF
condition is declared. Regardless of whether the F-bit value was correct or in error,
the F-bit counter is also incremented (after the value check), and if it reaches a value
of 16, both counters are reset and a new window of 16 F-bits is started. Therefore, if
one selects an arbitrary set of 16 F-bits and toggles the first bit, the 16th bit and one
bit in between, there is 1 in 16 chance that this set matches the Framer's fixed-
window set. This is therefore the chance of detection for a single such occurrence.
CX28342/3/4/6/8 Data Sheet
28348-DSH-001-B