QT2022/32 - Data Sheet: DS3051
The operations allowed by the pointer are listed below. Corresponding event flags are asserted high in Register
2.C000h:
1. positive stuff requires:
a) NDF=0110 (can support one bit corruption)
b) 3 or more I-bits inverted
c) less than 3 D-bits inverted
2. negative stuff requires:
a) NDF=0110 (can support one bit corruption)
b) 3 or more D-Bits inverted
c) less than 3 I-Bits inverted
3. pointer jump: there are 2 cases where the pointer can jump:
a) NDF = 1001 (can support one bit corruption) with 10 bits pointer in the range (0-782)
b) NDF =0110 (can support one bit corruption) with 3 consecutive frames with same 10 bits pointer value in
range (0-782)
Note: In the case where the pointer signaling indicates both positive and negative stuff operations, the logic considers this an invalid
pointer and ignores the pointer value.
The following list summarizes the rules for interpreting the pointer:
1. During normal operation, the pointer locates the start of the SPE (J1);
2. Any variation from the current pointer value is ignored unless a consistent new value is received three times
consecutively or it is preceded by one of rules 4,5 or 6. Any consistent new value received three times con-
secutively overrides (i.e. takes priority over) rules 4,5 or 6;
3. If the pointer value contains the Concatenation Value, then the operations performed on the STS-1 are identi-
cal to those performed on the first STS-1 within the STS-Nc. Operations 4 and 5 do not apply to this pointer
value.
4. If the majority of the I-bits of the pointer word are inverted, a positive stuff operation is indicated. Subsequent
pointer values are incremented by one;
5. If the majority of the D-bits of the pointer word are inverted, a negative stuff operation is indicated. Subsequent
pointer values are decremented by one;
6. If the New Data Flag is set to 1001, then the coincident pointer value will replace the current one at the offset
indicated by the new pointer value regardless of the state of the receive.
The QT2032 receive pointer processor can react to any change in the pointer value, for example, the receiver can
react to frame after frame of positive stuff, negative stuff.
Here are the cases where the pointer is considered as invalid:
1. NDF = 1001 with pointer value > 782
2. NDF = 0110 and consistent value is received 3 times consecutively with pointer value > 782
3. 2 bits corruption in the NDF bits.
4. The pointer value is asking for increment and decrement at the same time and value of the pointer > 782.
The QT2032 receive pointer processor checks the concatenation indicator in the H1H2 fields (after the first H1H2
bytes). A value of ‘93FF’ is expected. Any other value will cause a LOP-P condition. The SS bits must have a value
of ‘00’. In an SDH network, non-zero SS bits are allowed in the concatenation indicator. If non-zero values are used
in the concatenation indicator an LOP-P defect will be triggered.
If the pointer is invalid the bit 1 of register 2.32768 with be set to 1.
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