
XRT86SH221
PRELIMINARY
53
SDH-TO-PDH FRAMER/MAPPER WITH INTEGRATED 21-CHANNEL E1 SH LIU
REV. P1.0.5
STM-0/1 RECEIVE PATH PROCESSOR
RXSPOH_PROC BLOCK
The pointer processing operation of the rxspoh_proc block is described by the following SDH standard rules:
I
The pointer value shall be a binary number with a range of 0 to 782, and shall indicate the offset
between the pointer word (the last byte of the H3 field) and the first byte of the STS SPE.
I
A pointer increment operation shall be indicated by inverting the I-bits of the pointer word. The positive
stuff byte shall appear immediately after the H3 byte in the frame containing the inverted I-bits.
I
A pointer decrement operation shall be indicated by inverting the D-bits of the pointer word. The H3 byte
shall be used as the negative stuff byte, (i.e., it is used to carry an SPE byte in the frame containing the
inverted D-bits).
I
The increment/decrement decision should be made at the receiver by a match of 8 or more of the 10 I-
and D-bits to either the increment or decrement indication.
I
A normal NDF shall be indicated (during normal operation) by a '0110' code in the N-bits. The NDF shall
be set by inverting the N-bits to '1001'. The new alignment of the STS PSE shall be indicated by the
pointer value accompanying the set NDF and takes effect at the offset indicated.
I
The decoding at the pointer processor shall be performed by majority voting (i.e., the NDF shall be
detected as being set if three or four of the N-bits match the '1001' code). If a set NDF is detected, then
the coincident pointer value shall replace the current value at the offset indicated by the new pointer
value.
I
The first STM-0 within an STM-Nc shall have a normal pointer word
I
All subsequent STM-0s within the STM-Nc shall have their pointer values (i.e., bits 7 through 16) set to
all-ones, and their N-bits set to '1001' (i.e., set NDFs).
I
A pointer processor in an NE that is transmitting or receiving an STM-Nc SPE shall perform the
operations indicated by the pointer in the first STM-0 of the STM-Nc on all N of the STM-0s in that STM-
Nc.
I
During normal operation, the pointer value locates the start of the STS SPE within the STS Envelop
Capacity.
I
Any variation from the current pointer value shall be ignored unless a consistent new value is received
three times consecutively, or the variation is one of the operations in rules 4, 5, or 6.
I
Any consistent new value received three times in succession shall replace the current value at the offset
indicated by the new pointer value.
I
If the pointer word contains the concatenation indicator, then the operations performed on that STM-0
are identical to those performed on the first STM-0 within the STM-Nc. Rules 4 and 5 do not apply to this
pointer word.
I
If an increment is detected, then the byte following H3 shall be considered a positive stuff byte, and the
current pointer value shall be incremented by one.
I
If a decrement is detected, then H3 shall be considered a negative stuff byte, and the current pointer
value shall be decrement by one.
I
If a set NDF is detected, then the coincident pointer value replaces the current value at the offset
indicated by the new pointer value.
I
STS PTE and LTE that processes the STS pointer shall monitor for LOP-P. An LOP-P defect shall be
detected if a valid pointer is not found in N consecutive frames (where 8 is less than or equal to N less
than or equal to 10), or if N consecutive NDFs (other than in a concatenation indicator) are detected. An
LOP-P defect shall not be detected when LTE is receiving and relaying an all-ones STS pointer, or when
STS PTE is receiving pointers that qualify as those necessary to cause the detection of an AIS-P defect
(i.e., three or more consecutive all-ones pointers)
I
STS PTE and LTE that processes the STS pointers shall terminate an LOP-P defect when the STS has
a valid pointer with a normal NDF, or a valid concatenation indicator, in three consecutive frames.
I
STS PTE shall terminate an LOP-P defect when it detects an AIS-P defect.