XRT74L73 Datasheet, PDF (463/488 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 104: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
45
46
47
48
49
50
51
52
53
54
55
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT74L73
NR Byte - Bit 2
NR Byte - Bit 1
NR Byte - Bit 0
GC Byte - Bit 7
GC Byte - Bit 6
GC Byte - Bit 5
GC Byte - Bit 4
GC Byte - Bit 3
GC Byte - Bit 2
GC Byte - Bit 1
GC Byte - Bit 0
Figure 212 presents the typical behavior of the Re-
ceive Overhead Data Output Interface block, when
Method 1 is being used to sample the incoming E3
overhead bits.
FIGURE 212. THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD OUTPUT INTERFACE FOR METHOD 1.
RxOHClk
RxOHFrame
RxOH
FA1, Bit 7
FA1, Bit 6
FA1, Bit 5
FA1, Bit 4
FA1, Bit 3
Terminal Equipment should sample
the “RxOHFrame” and “RxOH” signals
here.
Recommended Sampling Edges
6.3.4.2 Method 2 - Using RxOutClk and the
RxOHEnable signals
Method 1 requires that the Terminal Equipment be
able to handle an additional clock signal, RxOHClk.
464