XRT74L73 Datasheet, PDF (167/488 Pages) Exar Corporation – 3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER

PRELIMINARY
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.0.1
block. However, if the RxUClav level is “low”, then
the ATM Layer processor should halt reading in
data, when it reaches the end of the cell (that it is
currently reading in).
• The ATM Layer processor should keep a count on
the total number of bytes that have been read in
since the last assertion of the RxUSoC output pin.
This will help the ATM Layer processor to determine
when it has reached the boundary of a given cell.
The previously-mentioned procedure is also depicted
in “Flow Chart Form” in Figure 40 , and in Timing
Diagram form in Figure 41 and 42.
FIGURE 40. FLOW CHART DEPICTING THE APPROACH THAT THE ATM LAYER PROCESSOR SHOULD TAKE WHEN
READING CELL DATA FROM THE RECEIVE UTOPIA INTERFACE, IN THE SINGLE-PHY MODE.
START
Check the level of the RxClav pin.
No
Is
RxClav
“High”?
Yes
Is this
the first byte
Yes
(word) of a new
cell?
No
READING IN THE FIRST BYTE/WORD
OF A CELL
Perform the following, concurrently
Assert the Receive Utopia Interface block
Output Enable input pin - RxEnB*.
Read in the first byte (word) from the
Receive Utopia Data Bus.
Read in the odd-parity value of this byte/
word from the RxPry output pin.
Check and verify that the RxSoC pin is
asserted.
READING IN THE REMAINING
BYTES/WORDS OF A CELL
Perform the following, concurrently
Assert the “Receive Utopia Data Bus Output
Enable input pin - RxEnB*.
Read in the next byte (word) from the
Receive Utopia Data Bus
Read in the odd-parity value of this byte
(word) from the RxPry output pin.
Is there
any more Cells
to read
Yes
?
No
END
Is the
No
current Cell
Yes
Complete?
168