DS2155 datasheet(104/238 Pages) DALLAS

104 / 238 page

DS2155

104 of 238

19.

ELASTIC STORES OPERATION

The DS2155 contains dual two-frame elastic stores, one for the receive direction and one for the transmit

direction. Both elastic stores are fully independent. The transmit and receive-side elastic stores can be

enabled/disabled independently of each other. Also, each elastic store can interface to either a 1.544MHz

or 2.048MHz/4.096MHz/8.192MHz/16.384MHz backplane without regard to the backplane rate the other

elastic store is interfacing to.

The elastic stores have two main purposes. Firstly, they can be used for rate conversion. When the

DS2155 is in the T1 mode, the elastic stores can rate-convert the T1 data stream to a 2.048MHz

backplane. In E1 mode, the elastic store can rate-convert the E1 data stream to a 1.544MHz backplane.

Secondly, they can be used to absorb the differences in frequency and phase between the T1 or E1 data

stream and an asynchronous (i.e., not locked) backplane clock, which can be 1.544MHz or 2.048MHz. In

this mode, the elastic stores manage the rate difference and perform controlled slips, deleting or repeating

frames of data in order to manage the difference between the network and the backplane.

The elastic stores can also be used to multiplex T1 or E1 data streams into higher backplane rates, which

is the IBO discussed in Section 28.

DS2155 Datasheet(PDF) 104 Page - Dallas Semiconductor