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XRT94L33
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC DATA SHEET
Rev.1.2.0.
169
XRT94L33 can be thought of as consisting of four ATM UNIs within a single package (one for each STS-3c
port within the device).
It is important to note that although the XRT94L33 consists of a single “Transmit UTOPIA Interface” block, the
XRT94L33 can be assigned four unique (4) Transmit UTOPIA Addresses as presented in Section
4.2.1.2.1.4.2.1.
2.2.1.3.11
Writing ATM Cell Data into a Different UNI
After the ATM Layer processor has “polled” each of the UNI devices, within its system, it must now select a
UNI, and begin writing ATM cell data to that device. The ATM Layer processor makes its selection and
begins the writing process by:
1.
Applying the UTOPIA Address of the “target” UNI on the “Transmit UTOPIA Address Bus”
(TxUAddr[4:0]).
Negate the TxUEnB* signal. This step causes the “addressed” UNI to recognize that it has been selected to
receive the next set of ATM cell data from the ATM Layer processor.
Assert the TxUEnB* signal.
Assert the TxUSoC input pin.
Begin applying the ATM Cell data in a byte-wide (or word-wide) manner to the Transmit UTOPIA Data Bus
(TxUData[15:0]).
At this point, ATM cell data is now being written into the TxFIFO associated with the newly selected UNI.
Figure 17 presents a flow-chart that depicts the “UNI Device Selection and Write” process in Multi-PHY
operation.
Figure 17: Flow-Chart of the “UNI Device Selection and Write Procedure” for the Multi-PHY Operation
START
Poll all UNIs within the “Multi-PHY” System.
Determine which UNIs are “Available”
Select “Available” UNI
1. Apply UTOPIA Address of the Transmit UTOPIA
Interface block onto the “UTOPIA Address” bus.
2. Negate the TxUEnB* signal
Begin writing ATM cell data into “Selected” UNI
1. Assert TxUEnB*
2. Place first byte/word of ATM cell onto the “Transmit
UTOPIA Data Bus & Assert TxUSoC
Continue to write ATM Cell data
Check the TxUClav level after
writing 48 bytes of cell data.
Is
TxUClav
“High”
?
Continue to poll UNI and
Wait for TxUClav to toggle “high”
Is
TxUClav
“High”
?
Is
there any more
ATM cell data to be
written to selected
UNI?
Yes
No
Yes
No
Figure 18 presents a timing diagram that illustrates the behavior of various “Transmit UTOPIA Interface block”
signals; during the “Multi-PHY” UNI Device Selection and Write operation.