XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
24
146
TxAddr4
I
Transmit UTOPIA Address Bus—MSB Input:
This input pin, along with TxAddr3
through TxAddr0 comprise the Transmit UTOPIA Address Bus input pins. The Trans-
mit UTOPIA Address Bus is only in use when the UNI is operating in the M-PHY
mode. When the ATM Layer processor wishes to write data to a particular UNI device,
it will provide the address of the “intended UNI” on the Transmit UTOPIA Address Bus.
The contents of the Transmit UTOPIA Address Bus input pins are sampled on the ris-
ing edge of TxClk. The DS3 UNI will compare the data on the Transmit UTOPIA
Address Bus with the pre-programmed contents of the TxUT Address Register
(Address = 70h). If these two values are identical and the TxENB pin is asserted, then
the TxClav pin will be driven to the appropriate state (based upon the TxFIFO fill level)
for the Cell Level handshake mode of operation.
147
TxAddr0
I
Transmit UTOPIA Address Bus Input—LSB:
(See Description for TxAddr4)
148
TxAddr3
I
Transmit UTOPIA Address Bus Input:
(See Description for TxAddr4)
149
TxAddr1
I
Transmit UTOPIA Address Bus Input:
(See Description for TxAddr4)
150
TxAddr2
I
Transmit UTOPIA Address Bus Input:
(See Description for TxAddr4)
151
TxClk
I
Transmit UTOPIA Interface Clock:
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 TxClk.
152
GND
***
Ground Signal Pin
153
GND
***
Ground Signal Pin
154
TxGFCMSB
O
Transmit GFC Nibble-Field Serial Input Port—MSB Indicator:
This signal, along with
TxGFC and TxGFCClk combine to function as the “Transmit GFC Nibble Field” serial
input port. This output signal will pulse “high” when the MSB (most significant bit) of
the GFC Nibble (for a given cell) is expected at the TxGFC input pin.
155
ResetB
I
Reset Input:
When this “active-low” signal is asserted, the UNI device will be asyn-
chronously reset. Additionally, all outputs will be “tri-stated”, and all on-chip registers
will be reset to their default values.
156
TxGFCClk
O
Transmit GFC Nibble Field Serial Input Port Clock:
This signal, along with TxGFC,
and TxGFCMSB combine to function as the “Transmit GFC Nibble-field” serial input
port. The “Transmit GFC Nibble-field” serial input port uses this output clock signal to
sample the values applied to the TxGFC pin, on its rising edge. This pin will provide
four rising edges for each cell being transmitted.
157
ALE_AS
I
Address Latch Enable/Address Strobe:
This input is used to latch the address
(present at the Microprocessor Interface Address Bus, A[8:0]) into the UNI Micropro-
cessor Interface circuitry and to indicate the start of a READ/WRITE cycle. This input
is active-high in the Intel Mode (MOTO = “l(fā)ow”) and active-low in the Motorola Mode
(MOTO = “high”).
158
TxGFC
I
Transmit GFC Nibble-Field Serial Input Port:
This signal, along with TxGFCClk and
TxGFCMSB combine to function as the “Transmit GFC Nibble-field” serial input port.
The user will specify the value of the GFC field, within a given ATM cell, by serial
transmitting its four bit value into this input. Each of these four bits will be clocked into
the UNI via rising edge of the TxGFCClk clock output signal.
159
GND
***
Ground Signal Pin
PIN DESCRIPTION (CONT’D)
P
IN
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O
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S
YMBOL
T
YPE
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ESCRIPTION