
XRT72L53
á
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
REV. P1.1.8
PRELIMINARY
329
Table 65 relates the number of rising clock edges (in
the RxOHClk signal, since the RxOHFrame signal
was last sampled "High”) to the E3 Overhead bit that
is being output via the RxOH output pin.
Figure 146 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.
TABLE 64: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (FOR METHOD 1)
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Data Output Interface block will output a given overhead bit, upon the
falling edge of RxOHClk. Hence, the external data link equipment should sample the data, at
this pin, upon the rising edge of RxOHClk.
NOTE: The XRT72L53 will always output the E3 Overhead bits via this output pin. There are no
external input pins or register bit settings available that will disable this output pin.
RxOHClk
Output
Receive Overhead Data Output Interface Clock Signal:
The XRT72L53 will output the Overhead bits (within the incoming E3 frames), via the RxOH
output pin, upon the falling edge of this clock signal.
As a consequence, the user's data link equipment should use the rising edge of this clock sig-
nal to sample the data on both the RxOH and RxOHFrame output pins.
NOTE: This clock signal is always active.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High” (for one period of the RxOHClk signal) whenever
the first overhead bit within a given E3 frame is being driven onto the RxOH output pin.
TABLE 65: 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
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected "High”)
FAS Pattern - Bit 9
1
FAS Pattern - Bit 8
2
FAS Pattern - Bit 7
3
FAS Pattern - Bit 6
4
FAS Pattern - Bit 5
5
FAS Pattern - Bit 4
6
FAS Pattern - Bit 3
7
FAS Pattern - Bit 2
8
FAS Pattern - Bit 1
9
FAS Pattern - Bit 0
10
A Bit
11
N Bit