XRT72L56 Datasheet, PDF (462/486 Pages) Exar Corporation – SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L56
SIX CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.2
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PRELIMINARY
FIGURE 210. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUT-
PUT INTERFACE BLOCK OF THE XRT72L56 AND THE TERMINAL EQUIPMENT
Terminal Equipment Signals
E3_Clock_In
E3_Data_In
Rx_Start_of_Frame
E3_Overhead_Ind
Payload[1522] Payload[1523]
FAS, Bit 9
FAS, Bit 8
XRT72L5x Receive Payload Data I/F Signals
RxClk
RxSer
Payload[1532] Payload[1533]
RxFrame
RxOH_Ind
FAS, Bit 9
FAS, Bit 8
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 FAS, A and N bits).
E3 Frame Number N + 1
Note: FAS, A and N-Bits will not be processed by the
Transmit Payload Data Input Interface.
6.3.5.2 Nibble-Parallel Mode OperationBehav-
ior of the XRT72L56
If the XRT72L56 has been configured to operate in
the Nibble-Parallel Mode, then the XRT72L56 will be-
have as follows.
Payload Data Output
The XRT72L56 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 XRT72L56 the Terminal Equip-
ment. The XRT72L56 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 XRT72L56 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 XRT72L56 the Terminal Equip-
ment.
Figure 211 presents a simple illustration as how the
user should interface the XRT72L56 to that terminal
equipment which processes Receive Direction pay-
load data.
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