
á
1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
PRELIMINARY
XRT79L71
REV. P1.0.3
15
C2
TxGFCClk
O
Transmit GFC Nibble-Field Serial Input port - Clock Output signal:
This signal, along with TxGFC and TxGFCMSB combine to function as the
Transmit GFC Nibble-field serial input port. This output signal functions as the
demand clock signal for this port. The user will specify the value of the GFC
field, within a given ATM cell, by serially transmitting its four bit-value into the
TxGFC input pin. The Transmit GFC Nibble-Field serial input port will latch the
contents of TxGFC upon the rising edge of this clock signal. Hence, the local ter-
minal equipment should be designed to place its outbound GFC bits on to the
TxGFC line, upon the falling edge of this clock signal.
N
OTE
:
This output pin is only active if the XRT79L71 has been configure to
operate in the ATM Mode.
B8
TxNib_3/
TxPOHIns/
TxHDLCDat_3
I
Transmit Nibble Interface - Bit 3/Transmit PLCP Path Overhead Insert
enable/Transmit HDLC Controller Data Bus - Bit 3 input:
The function of this input pin depends upon whether the XRT79L71 is configured
to operate in the Clear-Channel Framer Mode, the High-Speed HDLC Controller
Mode or in the ATM/PLCP Mode.
Clear-Channel Framer Mode - TxNib_3:
If the XRT79L71 is configured to operate in the Nibble-Parallel Mode, then this
input pin will function as the bit 3 (MSB) input to the Transmit Nibble-Parallel input
interface. The Transmit Payload Data Input Interface block will sample this signal
(along with TxNib_0 through TxNib_2) upon the falling edge of TxNibClk.
N
OTE
:
This input pin is inactive if the XRT79L71 is configured to operate in the
Serial Mode.
ATM/PLCP Mode - TxPOHIns:
f the XRT79L71 is configured to operate in the ATM Mode, and if (within the ATM
Mode, the chip is also configured to operate in the PLCP Mode), then this input
pin functions as the Transmit PLCP Path Overhead Port - Enable input pin. In
this mode, the user can externally insert desired path overhead byte values into
the outbound PLCP frames.
The Transmit PLCP Path Overhead Input port becomes active whenever the user
asserts this input pin by pulling it "High". Once this occurs, the data, residing
upon the TxPOH input pin will be sampled upon the rising edge of the TxPOHClk
signal.
This input pin is inactive if the XRT79L71 is configured to operate in the Direct-
Mapped ATM Mode.
High-Speed HDLC Controller Mode - TxHDLCDat_3:
If the XRT79L71 is configured to operate in the High-Speed HDLC Controller
mode, then the local terminal equipment will be provided with a byte-wide Trans-
mit HDLC Controller byte-wide input interface. This input pin will function as Bit 3
within this byte wide interface.
Data, residing on the Transmit HDLC Controller byte wide input interface, will be
sampled upon the rising edge of the TxHDLCClk output signal.
P
IN
#
N
AME
TYPE
D
ESCRIPTION