XRT59L91 Datasheet, PDF (17/28 Pages) Exar Corporation – Single-Chip E1 Line Interface Unit

Preliminary
XRT59L91
Timing Requirements associated with Declaring
and Clearing the LOS Indicator.
The XRT59L91 device was designed to meet the ITU-
T G.775 specification timing requirements for declar-
ing and clearing the LOS indicator. In particular, the
XRT59L91 device will declare LOS, between 10 and 255
UI (or E1 bit-periods) after the actual time the LOS
condition occurred. Further, the XRT59L91 device will
clear the LOS indicator within 10 to 255 UI after
restoration of the incoming line signal. Figure 11
illustrates the LOS Declaration and Clearance behav-
ior, in response to first, the “Loss of Signal” event and
then afterwards, the restoration of the signal.
RXIN
Actual
O cocfuLrrOeSn ce
C o n d itio n
Line
S igisn a l
R e s to re d
10 UI
255 UI
Tim e Range
LfoOrS
D e c la ra tio n
LOS Output Pin
0
UI
Note: For E1, 1 UI = 488ns
G .775 Com pliance
10 UI
255 UI
0
UI
Tim e Range
LfOo rS
C le a ra n c e
G .775 Com pliance
Figure 11. The Behavior of the LOS Output Indicator, in response to the Loss of Signal,
and the Restoration of the Signal
2.5 The “Receive Output Interface” Block
The purpose of the “Receive Output Interface” block is
to interface directly with the “Receiving Terminal
Equipment”. The “Receive Output Interface” block
outputs the data (which has been recovered from the
incoming line signal) to the “Receive Terminal Equip-
ment” via the “RxPOS and RxNEG output pins.
If the “Receive Section” of the XRT59L91 device has
received a “Positive-Polarity” pulse, via the RTIP and
RRing input pins, then the Receive Output Interface will
output a pulse at the “RxPOS” output pin.
Similarly, if the “Receive Section” of the XRT59L91
device has received a “Negative-Polarity” pulse, via
the RTIP and RRing input pins, then the Receive Output
Interface will output a pulse at the “RxNEG” output pin.
Rev. P2.00
17