XRT7250 Datasheet, PDF (445/463 Pages) Exar Corporation – DS3/E3 FRAMER IC

XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Ter-
minal Equipment
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The behavior of the signals between the XRT7250
and the Terminal Equipment for E3 Serial Mode Op-
eration is illustrated in Figure 210.
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
Payload[4238] Payload4239]
FA1, Bit 7
FA1, Bit 6
XRT7250 Receive Payload Data I/F Signals
RxClk
RxSer
Payload[4238] Payload[4239]
RxFrame
RxOH_Ind
FA1, Bit 7
FA1, Bit 6
E3 Frame Number N
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).
E3 Frame Number N + 1
Note: FA1 and FA2 bytes will not be processed by the
Transmit Payload Data Input Interface.
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.
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