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XRT79L71
PRELIMINARY
295
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
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
TABLE 39: LIST AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT OVERHEAD DATA INPUT
INTERFACE BLOCK
SIGNAL NAME
PIN/BALL
NUMBER
TYPE
DESCRIPTION
TxOHEnable
A12
O
Transmit Overhead Data - Enable Output Pin:
The Transmit Overhead Data Input Interface will assert this signal (e.g., pulse
it "High") for one TxInClk period, just prior to the instant that it (the Transmit
Overhead Data Input Interface block) is processing an overhead bit.
NOTE: This output pin will remain "Low" at all other times.
TxInClk
C10
I
Transmit Section - Timing Reference Clock Input Pin:
If the XRT79L71 has been configured to operate in the Local-Timing Mode,
then this input pin will function as the timing source for the Transmit Circuitry
within the XRT79L71.
TxOHFrame
B11
O
Transmit Overhead Input Interface Enable Input Pin:
This output pin pulses "High" whenever the Transmit Overhead Data Input
Port is processing the last bit within a given E3 frame.
TxOHIns
D10
I
Transmit Overhead Data - Insert Enable Input Pin:
Asserting this input pin (e.g., setting it "High") enables the Transmit Overhead
Data Input Interface to accept overhead data from the System-Side Terminal
Equipment. In other words, while this input pin is "High", the Transmit Over-
head Data Input Interface will sample the data on the TxOH input pin, upon
the falling edge of either the TxInClk or the TxOHClk clock signals.
Setting this input pin "Low" configures the Transmit Overhead Data Input
Interface block to NOT sample (e.g., ignore) the data on the TxOH input pin
upon the falling edge of either the TxInClk or the TxOHClk clock signals.
NOTE: If the System-Side Terminal Equipment attempts to insert an overhead
bit that cannot be accepted by the Transmit Overhead Data Input
Interface block (e.g., if the System-Side Terminal Equipment asserts
the TxOHIns input pin at a time whenever one of the non-insertable
overhead bits are being processed), then this particular insertion
effort will be ignored.
TxOH
C11
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-posi-
tion within the very next outbound E3 frame. If the "TxOHIns" input pin is
pulled "high", then the Transmit Overhead Data Input Interface block will sam-
ple the data, residing on this input pin, upon either the rising edge of TxInClk
or the falling 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 rising edge of "TxInClk" nor on the falling edge of "TxOHClk".
TxOHClk
B12
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
Interface block will sample and latch the data (residing on the "TxOH" input
pin) upon the falling edge of this signal.