XR72L52 Datasheet, PDF (241/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L52
REV. 1.0.1
FIGURE 82. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK OF THE XRT72L52 AND THE TERMINAL EQUIPMENT (SERIAL MODE OPERATION)
Terminal Equipment Signals
DS3_Clock_In
DS3_Data_In
Rx_Start_of_Frame
DS3_Overhead_Ind
Payload[4702] Payload[4703]
X-Bit
Payload[0]
XRT72L5x Receive Payload Data I/F Signals
RxClk
RxSer
Payload[4702] Payload[4703]
RxFrame
RxOH_Ind
X-Bit
Payload[0]
DS3 Frame Number N
Note: RxFrame pulses high to denote
DS3 Frame Boundary.
Note: RxOH_Ind pulses high to
denote Overhead Data
(e.g., the X-bit).
DS3 Frame Number N + 1
Note: X-Bit will not be processed by the
Transmit Payload Data Input Interface.
4.3.5.2 Nibble-Parallel Mode Operation
Behavior of the XRT72L52
If the XRT72L52 has been configured to operate in the Nibble-Parallel Mode, then the XRT72L52 will behave
as follows.
Payload Data Output
The XRT72L52 will output the payload data of the incoming DS3 frames, via the RxNib[3:0] output pins, upon
the falling edge of RxClk.
NOTES:
1. In this case, RxClk will function as the Nibble Clock signal between the XRT72L52 the Terminal Equipment. The
XRT72L52 will pulse the RxClk output signal "High" 1176 times, for each inbound DS3 frame.
2. Unlike Serial Mode operation, the duty cycle of RxClk, in Nibble-Parallel Mode operation is approximately 25%.
Delineation of Inbound DS3 Frames
The XRT72L52 will pulse the RxFrame output pin "High" for one nibble-period coincident with it driving the very
first nibble, within a given inbound DS3 frame, via the RxNib[3:0] output pins.
Interfacing the XRT72L52 the Terminal Equipment.
Figure 83 presents a simple illustration as how the user should interface the XRT72L52 to that terminal equip-
ment which processes Receive Direction payload data.
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