XRT79L72 Datasheet, PDF (24/72 Pages) Exar Corporation – 2 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

XRT79L72
REV. P1.0.2
PIN #
B10
NAME
TxUClk/
TxPClk
PRELIMINARY
xr
2 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
TYPE
DESCRIPTION
I Transmit UTOPIA Interface Clock/Transmit POS-PHY Interface Clock Input:
The function of this input pin depends upon whether the XRT79L72 has been
configured to operate in the ATM UNI or in the PPP Mode.
ATM UNI Mode - TxUClk:
The Transmit UTOPIA Interface clock is used to latch the data on the Transmit
UTOPIA Data bus, into the Transmit UTOPIA Interface block. This clock signal
is also used as the timing source for circuitry used to process the ATM cell data
into and through the TxFIFO.
During Multi-PHY operation, the data on the Transmit UTOPIA Address bus pins
is sampled on the rising edge of TxUClk.
PPP Mode - TxPClk:
The Transmit POS-PHY Interface clock is used to latch the data on the Transmit
POS-PHY Data bus, into the Transmit POS-PHY Interface block. This clock sig-
nal is also used as the timing source for circuitry used to process the Packet data
into and through the TxFIFO.
NOTE: The XRT79L72 device can support TxUClk or TxPClk clock frequencies
of up to 50MHz.
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