XRT74L73 Datasheet, PDF (38/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
PRELIMINARY
PIN DESCRIPTION
PIN#
AE14
NAME
TxUPrty/TxPPrty
AC9 TxUSoC/TxPSOP
TYPE
I
I
DESCRIPTION
Transmit UTOPIA Data Bus - Parity Input/Transmit POS-PHY Interface -
Parity Input:
The exact function of this input pin depends upon whether the XRT74L73 device
has been configured to operate in the ATM UNI or PPP Mode.
ATM UNI Mode - TxUPrty:
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., TxUData[7:0] or TxU-
Data[15:0]) inputs of the XRT74L73, respectively.
NOTE: This parity 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 XRT74L73 device) 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.
PPP Mode - TxPPrty:
The Link Layer Processor will apply the parity value of the byte or word which is
being applied to the Transmit POS-PHY Data Bus (e.g., TxPData[7:0] or TxP-
Data[15:0]) inputs of the XRT74L73, respectively.
NOTE: This parity value should be computed based upon the odd-parity of the
data applied to the Transmit POS-PHY Data Bus. The Transmit POS-PHY Inter-
face block (within the XRT74L73 device) will independently compute an odd-par-
ity value of each byte (or word) that it receives from the Link Layer processor
and will compare it will the logic level of this input pin.
Transmit UTOPIA - Start of Cell Input/Transmit POS-PHY - Start of Packet
Input:
The exact function of this input signal depends upon whether the XRT74L73
device has been configured to operate in the ATM UNI or in the PPP Mode.
ATM UNI Mode Operation - TxUSoC
This input pin is driven by the ATM Layer Processor and is used to indicate the
start of an ATM cell that is being transmitted from the ATM Layer Processor.
This input pin must be pulsed "high" whenever the first byte (or word) of a new
cell is present on the Transmit UTOPIA Data Bus (TxUData[15:0]). This input
pin must remain "low" at all other times.
PPP Mode Operation - TxPSoP/TxPSoC
If the XRT74L73 device has been configured to operate in the "Packet-Mode",
then this input pin is pulsed "high" to denote that the first byte (or word) of a
given packet is placed on the "TxPData[15:0]" input pins.If the XRT74L73 device
has been configured to operate in the Cell-Chunk Mode, then this input pin is
pulsed "high" to denote that the first byte of a packet chunk, if placed on the
"TxPData[15:0]" input pins.
NOTE: This input pin is only valid if the XRT74L73 device has been configured to
operate in the PPP Mode.
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