ort8850 Lattice Semiconductor Corp., ort8850 Datasheet - Page 43

• Manufacturer Part Number: ort8850
• Description: Field-programmable System Chip Fpsc Eight-channel X 850 Mbits/s Backplane Transceiver
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Table 13. Valid Starting Positions for and STS MC (Continued)
A pointer action byte (H3) is allocated for SPE frequency justification purposes. Frequency justification is discussed
in a later section. The H3 byte is used in all STS-1s within an STS-N to carry the extra SPE byte in the event of a
negative pointer adjustment. The value contained in this byte when it's not used to carry the SPE byte is undefined.
Pointer Interpreter State Machine.
The pointer interpreter's highest priority is to maintain accurate data flow (i.e., valid SPE only) into the elastic store.
This will ensure that any errors in the pointer value will be corrected by a standard, fully SONET compliant, pointer
interpreter without any data hits. This means that error checking for increment, decrement, and new data flag
(NDF) (i.e., 8 of 10) is maintained in order to ensure accurate data flow. A single valid pointer (i.e., 0-782) that dif-
fers from the current pointer will be ignored. Two consecutive incoming valid pointers that differ from the current
pointer will cause a reset of the J1 location to the latest pointer value (the generator will then produce an NDF).
This block is designed to handle single bit errors without affecting data flow or changing state.
The pointer interpreter has only three states (NORM, AIS, and CONC). NORM state will begin whenever two con-
secutive NORM pointers are received. If two consecutive NORM pointers that both differ from the current offset are
received, then the current offset will be reset to the last received NORM pointer. When the pointer interpreter
changes its offset, it causes the pointer generator to receive a J1 value in a new position. When the pointer gener-
ator gets an unexpected J1, it resets its offset value to the new location and declares an NDF. The interpreter is
only looking for two consecutive pointers that are different from the current value. These two consecutive NORM
pointers do not have to have the same value. For example, if the current pointer is ten and a NORM pointer with off-
set of 15 and a second NORM pointer with offset of 25 are received, then the interpreter will change the current
pointer to 25.
If the data is concatenated, the receipt of two consecutive CONC pointers causes CONC state to be entered. Once
in this state, offset values from the head of the concatenation chain are used to determine the location of the STS
SPE for each STS in the chain. Finally, if two consecutive AIS pointers cause the AIS state to occur. Any two con-
secutive normal or concatenation pointers will end this AIS state. This state will cause the data leaving the pointer
generator to be overwritten with 0xFF.
Figure 22. Pointer Mover State Machine
Note:
Yes = STS-Mc SPE can start in that STS-1.
No = STS-Mc SPE cannot start in that STS-1.
-
Number
= Yes or no, depending on the particular value of M.
STS-1
46
STS-3cSPE
Yes
STS-6cSPE
No
CONC
STS-9cSPE
No
2 x CONC
2 x AIS
Norm
43
STS-12cSPE
No
AIS
ORCA ORT8850 Data Sheet
STS-15cSPE
No
STS-18c to
STS-48c
SPEs
No