XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
22
121
TxOHClk
O
Transmit DS3 Framer Overhead Bit Serial Input Port—clock signal output.
This
output clock signal, along with the TxOH, TxOHFrame, and TxOHIns pins, comprise
the “Transmit DS3 Framer OH Bits” serial input port. When this serial port is active,
then the data applied to the TxOH input pin will be “l(fā)atched” into the serial port on the
rising edge of this clock signal.
Note:
The TxOHClk signal is always active whether the “TxOH Serial Input” port is
active or not.
122
TxOHFrame
O
Transmit DS3 Framer Overhead Bit Serial Input Port—framing signal indicator.
This output signal, along with the TxOH, TxOHClk and TxOHIns pins comprise the
“Transmit DS3 Framer OH Bits” serial input port. This output pin pulses “high” when
the value for the first “X” bit (in F-Frame #1) is expected at the TxOH input pin.
Note:
This output pin is always active whether the “Transmit DS3 Framer OH Serial
Input” port is active or not.
123
TxEnB*
I
Transmit UTOPIA Interface Block—Write Enable:
This active-low signal, from the
ATM Layer processor enables the data on the Transmit UTOPIA Data Bus to be written
into the TxFIFO on the rising edge of TxClk. When this signal is asserted, then the
contents of the byte or word that is present, on the Transmit UTOPIA Data Bus, will be
latched into the Transmit UTOPIA Interface block, on the rising edge of TxClk.
When this signal is negated, then the Transmit UTOPIA Data bus inputs will be tri-
stated.
124
TxSoC
I
Transmitter—Start of Cell (SoC) Indicator Input:
This input pin is driven by the ATM
Layer processor and is used to indicate the start of an ATM cell that is being transmit-
ted from the ATM layer processor. This input pin must be pulsed “high” when the first
byte (or word) of a new cell is present on the Transmit UTOPIA Data Bus. This input
pin must remain “l(fā)ow” at all other times.
125
TxPrty
I
Transmit UTOPIA Data Bus—Parity Input:
The ATM Layer processor will apply the
parity value of the byte or word which is being applied to the Transmit UTOPIA Data
Bus (e.g., TxData[7:0] or TxData[15:0]) inputs of the UNI, respectively. Note: this par-
ity value should be computed based upon the odd-parity of the data applied at the
Transmit UTOPIA Data Bus. The Transmit UTOPIA Interface block (within the UNI) will
independently compute an odd-parity value of each byte (or word) that it receives from
the ATM Layer processor and will compare it with the logic level of this input pin.
PIN DESCRIPTION (CONT’D)
P
IN
N
O
.
S
YMBOL
T
YPE
D
ESCRIPTION