DS21Q55N Maxim Integrated Products, DS21Q55N Datasheet - Page 108

• Manufacturer Part Number: DS21Q55N
• Description: Framer E1/J1/T1 3.3V 256-Pin BGA
• Manufacturer: Maxim Integrated Products

Specifications of DS21Q55N

• Package: 256BGA
• Number Of Transceivers: 4
• Standard Framing Format: E1|J1|T1
• Maximum Supply Current: 75(Typ) mA
• Minimum Single Supply Voltage: 3.135 V
• Maximum Single Supply Voltage: 3.465 V

DS21Q55 Quad T1/E1/J1 Transceiver
17.
ELASTIC STORES OPERATION
The DS21Q55 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 device
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 26.
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