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XRT79L71
PRELIMINARY
101
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
The purpose of the Transmit Overhead Data Input Interface block is to accept overhead data from some
system-side or up-stream source and to overwrite the contents of the overhead bits, within the outbound DS3
data-stream with these particular overhead bit values.
In order to accomplish this, the Transmit Overhead Data Input Interface block has numerous input and output
pins. Table 19 presents a list and a brief definition of each of these pins.
TABLE 19: 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 the Transmit Over-
head Data Input Interface block is processing an overhead bit.
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 DS3 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 Overhead
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 Inter-
face 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.