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PRELIMINARY
XRT79L71
102
REV. P2.0.0
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
The Two Methods of Inserting Overhead Data Into the Transmit Overhead Data Input Interface Block
There are two methods that can be used to insert the overhead data into the Transmit Overhead Data Input
Interface Block. One Method is referred to as Method 1 or the TxOHClk Method, and the other method is
referred to as Method 2 or the TxInClk Method. Each of these methods is described in considerable detail
below.
4.2.2.1
Operating the Transmit Overhead Data Input Interface using Method 1 - The TxOHClk
Method
This particular method is referred to as the TxOHClk method for the following reasons.
a. The System-Side Terminal Equipment will use the TxOHClk clock output signal from the Transmit
Overhead Data Input Interface block to clock overhead data onto the TxOH input pin.
b. The Transmit Overhead Data Input Interface block will use the falling edge of the TxOHClk clock output
signal to sample and latch the data residing on the TxOH input pin.
If Method 1 is used, the System-Side Terminal Equipment will need to interface to the following Transmit
Overhead Data Input Interface pins.
TxOH
TxOHClk
TxOHFrame
TxOHIns
If Method 1 is used the users system must be designed such that the System-Side Terminal Equipment will be
interfaced to the Transmit Overhead Data Input Interface block, in a manner as presented below in Figure 44.
TxOH
C11
I
Transmit Overhead Data Input Interface - Overhead Data Input Pin:
The Transmit Overhead Data Input Interface block accepts the overhead data
via this input pin and inserts this data into the appropriate overhead bit-position
within the very next outbound DS3 frame. If the TxOHIns input pin is pulled
"High", then the Transmit Overhead Data Input Interface block will sample the
data, residing on this input pin, upon either the rising edge of TxInClk or the fall-
ing edge of TxOHClk depending upon the Insertion Method used.
If the TxOHIns input pin is pulled "Low", then the Transmit Overhead Data Input
Interface block will NOT sample the data, residing on this input pin, upon the ris-
ing edge of TxInClk nor on the falling edge of TxOHClk.
TxOHClk
B13
O
Transmit Overhead Clock Output:
This output pin functions as the "Transmit Overhead Data Input Interface" clock
signal. If the Transmit Overhead Data Input Interface block is enabled by
asserting the TxOHIns input pin, then the Transmit Overhead Data Input Inter-
face block will sample and latch the data (residing on the "TxOH" input pin)
upon the falling edge of this signal.
TABLE 19: LIST AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT OVERHEAD DATA INPUT
INTERFACE BLOCK
SIGNAL NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION