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PRELIMINARY
XRT79L71
470
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
Figure 224, the System-Side Terminal Equipment samples the TxOHFrame and TxOHEnable output pins
being "High" during Falling Clock Edge # 0 within the TxInClk signal. At this point, the System-Side Terminal
Equipment know that the XRT79L71 is just about to process the very first overhead bit within a given outbound
E3 frame.
In order to facilitate the transmission of the FERF/RDI indicator, the System-Side Terminal
Equipment must set the FERF/RDI bit-field within the outbound E3 frame to "1". According to Table 61, the
FERF/RDI bit-field will be ready for processing coincident to the 32nd assertion of the TxOHEnable output
signal, following the most recent assertion of TxOHFrame.
The System-Side Terminal Equipment can externally set the FERF/RDI bit-field within each outbound E3 frame
to "1" by implementing the following tasks in the sequence as depicted below.
TASK # 1 - Continuously sample both the TxOHFrame and the TxOHEnable output pins with each falling edge
of TxInClk. Whenever the System-Side Terminal Equipment samples both of these input pin "High", then it
should move on to TASK # 2.
TASK # 2- Continue to sample both the TxOHEnable and TxOHFrame output pins with each falling edge of
TxInClk. The System-Side Terminal Equipment should increment an internal counter each time it samples the
TxOHEnable output pin "High".
The System-Side Terminal Equipment should execute this task until the
counter has reach the value "32".
Once this counter has reached the value "32" then the System-Side
Terminal Equipment should move on to TASK # 3.
TASK # 3 - The System-Side Terminal Equipment MUST execute all of the following two sub-tasks
simultaneously.
FIGURE 224. ILLUSTRATION OF THE SIGNALING THAT MUST OCCUR BETWEEN THE SYSTEM-SIDE TERMINAL EQUIP-
MENT AND THE
TRANSMIT OVERHEAD DATA INPUT INTERFACE OF THE XRT79L71, IN ORDER TO CONFIGURE THE
XRT79L71 TO TRANSMIT THE FERF/RDI INDICATOR TO THE REMOTE TERMINAL EQUIPMENT (USING METHOD 2)
TxInClk
TxOHFrame
TxOHEnable
TxOHIns
TxOH
System-Side Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
System-Side Terminal Equipment
responds by waiting for the “TxOHEnable” output
Pin to pulse 32 more times prior to asserting TxOHIns
and placing desired data on TxOH.
XRT79L71 device samples TxOH
here.
TxOHEnable Pulse # 32
FERF bit = 1
0
2
3
A
B
TxOHEnable Pulse # 0