XRT79L74 Datasheet, PDF (41/70 Pages) Exar Corporation – 4 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

PRELIMINARY
4 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
XRT79L74
REV. P1.0.0
PIN #
A17
B17
C17
E17
A18
B18
C18
A19
B19
C19
D19
A20
B20
C20
A21
B21
B13
NAME
RxUData_0/
RxPData_0
RxUData_1/
RxPData_1
RxUData_2/
RxPData_2
RxUData_3/
RxPData_3
RxUData_4/
RxPData_4
RxUData_5/
RxPData_5
RxUData_6/
RxPData_6
RxUData_7/
RxPData_7
RxUData_8/
RxPData_8
RxUData_9/
RxPData_9
RxUData_10/
RxPData_10
RxUData_11/
RxPData_11
RxUData_12/
RxPData_12
RxUData_13/
RxPData_13
RxUData_14/
RxPData_14
RxUData_15/
RxPData_15
RxMod
TYPE
O
DESCRIPTION
Receive UTOPIA Data Bus Input/Receive POS-PHY Data Bus Output pins:
The function of these output pins depends upon whether the XRT79L74 has
been configured to operate in the ATM UNI or in the PPP Mode.
ATM UNI Mode - RxUData[15:0]:
These output pins function as the Receive UTOPIA Data Bus. ATM cell data
that has been received from the Remote Terminal Equipment is output on the
Receive UTOPIA Data Bus, where it can be read and processed by the ATM
Layer Processor.
PPP Mode - RxPData[15:0]:
These output pins function as the Receive POS-PHY Data Bus output pins.
PPP Packet data that has been received from the Remote Terminal Equipment
is output on the Receive POS-PHY Data Bus, where it can be reads and pro-
cessed by the Link Layer Processor.
O Receive PPP Data Bus - Modulus Indicator:
The XRT79L74 will indicate the number of valid packet octets that are being
read out of the RxPData[15:0] output pins.
The XRT79L74 will drive this output pin "Low" when both bytes of the RxP-
Data[15:0] data bus consists of valid packet data.
Conversely, the XRT79L74 will drive this output pin "High" when only the upper
byte of the RxPData[15:0] data bus consists of valid packet data.
The Link Layer Processor is expected to validate all packet data that it reads out
of the RxPData[15:0] output pins by also reading the state of this output pin.
NOTE: This output pin is only active if the XRT79L74 has been configured to
operate in the PPP Mode.
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