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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
428
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method 2)
Figure 193 illustrates how one should interface the Receive Overhead Data Output Interface block to the
Terminal Equipment, when using Method 2 to sample and process the overhead bits from the Inbound E3 data
stream.
Method 2 Operation of the Terminal Equipment
If the Terminal Equipment intends to sample any overhead data from the Inbound E3 data stream (via the
Receive Overhead Data Output Interface), then it is expected to do the following.
TABLE 86: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (METHOD 2)
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L50 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Output Interface will pulse the RxOHEnable output pin (for one RxOut-
Clk period) at approximately the middle of the RxOH bit period. The user is advised to design
the Terminal Equipment to latch the contents of the RxOH output pin, whenever the RxOHEn-
able output pin is sampled "High" on the falling edge of RxOutClk.
RxOHEnable
Output
Receive Overhead Data Output Enable - Output pin:
The XRT72L50 will assert this output signal for one RxOutClk period when it is safe for the
Terminal Equipment to sample the data on the RxOH output pin.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L50 will drive this output pin "High" (for one period of the RxOH signal), whenever
the first overhead bit, within a given E3 frame is being driven onto the RxOH output pin.
RxOutClk
Output
Receive Section Output Clock Signal:
This clock signal is derived from the RxLineClk signal (from the LIU) for loop-timing applica-
tions, and the TxInClk signal (from a local oscillator) for local-timing applications. For E3 appli-
cations, this clock signal will operate at 34.368MHz.
The user is advised to design the Terminal Equipment to latch the contents of the RxOH pin,
anytime the RxOHEnable output signal is sampled "High" on the falling edge of this clock sig-
nal.
FIGURE 193. THE TERMINAL EQUIPMENT BEING INTERFACED TO THE RECEIVE OVERHEAD DATA OUTPUT INTER-
FACE
(METHOD 2)
E3_OH_In
E3_OH_Enable_In
E3_Clk_In
Rx_Start_of_Frame
RxOH
RxOHEnable
RxOutClk
RxOHFrame
Terminal Equipment
E3 Framer