XRT7250 datasheet(445/463 Pages) EXAR

445 / 463 page

XRT7250

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DS3/E3 FRAMER IC

REV. 1.1.1

426

The Behavior of the Signals between the Receive

Payload Data Output Interface block and the Ter-

minal Equipment

The behavior of the signals between the XRT7250

and the Terminal Equipment for E3 Serial Mode Op-

eration is illustrated in Figure 210.

6.3.5.2

Nibble-Parallel Mode OperationBehav-

ior of the XRT7250

If the XRT7250 has been configured to operate in the

Nibble-Parallel Mode, then the XRT7250 will behave

as follows.

Payload Data Output

The XRT7250 will output the payload data of the in-

coming E3 frames, via the RxNib[3:0] output pins, up-

on the rising edge of RxClk.

NOTES:

1. In this case, RxClk will function as the Nibble Clock

signal between the XRT7250 the Terminal Equip-

ment. The XRT7250 will pulse the RxClk output

signal "High" 1060 times, for each Inbound E3

frame.

2. Unlike Serial Mode operation, the duty cycle of

RxClk, in Nibble-Parallel Mode operation is approx-

imately 25%.

Delineation of Inbound DS3 Frames

The XRT7250 will pulse the RxFrame output pin

"High" for one nibble-period coincident with it driving

the very first nibble, within a given Inbound E3 frame,

via the RxNib[3:0] output pins.

Interfacing the XRT7250 the Terminal Equipment.

Figure 211 presents a simple illustration as how the

user should interface the XRT7250 to that terminal

equipment which processes Receive Direction pay-

load data.

FIGURE 210. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUT-

PUT

INTERFACE BLOCK OF THE XRT7250 AND THE TERMINAL EQUIPMENT

Terminal Equipment Signals

E3_Clock_In

E3_Data_In

Rx_Start_of_Frame

E3_Overhead_Ind

XRT7250 Receive Payload Data I/F Signals

RxClk

RxSer

RxFrame

RxOH_Ind

Payload[4238]

Payload4239]

FA1, Bit 7

FA1, Bit 6

Payload[4238]

Payload[4239]

FA1, Bit 7

FA1, Bit 6

Note: FA1 and FA2 bytes will not be processed by the

Transmit Payload Data Input Interface.

E3 Frame Number N

E3 Frame Number N + 1

Note: RxFrame pulses high to denote

E3 Frame Boundary.

Note: RxOH_Ind pulses high to

denote Overhead Data

(e.g., the FA1 and FA2 Bytes).

XRT7250 Datasheet(PDF) 445 Page - Exar Corporation

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