CN8223 Datasheet, PDF (73/161 Pages) Conexant Systems, Inc – ATM Transmitter/Receiver with UTOPIA Interface

CN8223
ATM Transmitter/Receiver with UTOPIA Interface
2.0 Functional Description
2.7 FIFO Port/UTOPIA Interface
Table 2-24. FIFO Transmit Pin Functional Descriptions
CN8223 FIFO Pin Function
Functional Description
Transmit Data FIFO Empty
Transmit PLCP Frame Sync
Transmit Start of Cell Marker
Transmit Cell Sync Marker
In the transmit direction, the Transmit Data FIFO Empty input inhibits the Transmit Data Read
Strobe for a particular port. The empty flag from the FIFO, when inactive, indicates that the
FIFO contains at least one entire cell of the appropriate length for the selected mode. Data read
strobes to a particular port are inhibited if the empty flag for that port is low. There are four of
these signals, asserted low, one per port.
If using FIFO mode and PLCP mapping, when 57-octet input is selected on the transmitter, the
Transmit PLCP Frame Sync Marker (FCTRL_OUT[16]) is high during the first slot of the PLCP
frame to indicate the start of the frame.
In 53-octet mode, FCTRL_OUT[16] indicates the Transmit Start of Cell, informing the FIFO that
the next strobe will read the first octet of the cell to be transmitted.
The Transmit Cell Sync Marker is an additional output to delineate cell boundaries to the
transmit data FIFO. This marker is low during the read strobe requesting the last octet of a cell,
and high during all other read strobes regardless of the programmed length of the cell to be
transferred from the FIFO.
Figure 2-17. Receive FIFO Port Interface Timing, 53-Octet Mode
Port X Receive
Data Write Strobe
Receive Cell
Sync Marker
Receive Start-
of-Cell Marker
Receive Cell
Invalid Indication
Receive Data Octet
56 0 1 2 3 4
•••
55 56 0
100046C
Conexant
2-39