XRT74L73 Datasheet, PDF (261/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
TABLE 58: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT74L73
46
UDL
47
F1
48
M0
49
F1
50
UDL
51
F0
52
UDL
53
F0
54
UDL
55
F1
Figure 96 presents the typical behavior of the Re-
ceive Overhead Data Output Interface block, when
Method 1 is being used to sample the incoming DS3
overhead bits.
FIGURE 96. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD OUTPUT INTERFACE
(FOR METHOD 1).
RxOHClk
RxOHFrame
RxOH
X
F1
AIC
F0
FEAC
Terminal Equipment should sample
the “RxOHFrame” and “RxOH” signals
here.
Recommended Sampling Edges
Method 2 - Using RxOutClk and the RxOHEnable
signals
Method 1 requires that the Terminal Equipment be
able to handle an additional clock signal, RxOHClk.
However, there may be a situation in which the Termi-
nal Equipment circuitry does not have the means to
accommodate and process this extra clock signal, in
order to use the Receive Overhead Data Output In-
terface. Hence, Method 2 is available. Method 2 in-
volves the use of the following signals.
262