PXB4219 Datasheet, PDF (109/290 Pages) Infineon Technologies AG – IWE8 Interworking Element for 8 E1/T1 Lines

PXB4219 / PXB4220 / PXB4221
Interface Description
5.2.2.2 Port Specific Backpressure Mechanism
In addition to the general backpressure mechanism, port specific backpressure is
available for ATM ports, when using the IWE8 as a UTOPIA level 2 PHY device
(“utconf[utlevel]” =0, “utmaster” = 0, “mapping_mode” =0 and “pcfN[p_atm]” =1). It needs
to be explicitly enabled with the “p_thr_m” bits in the “Port Configuration Registers”
(“pcfN”, see Chapter 7.1).
Whenever the port transmit buffer filling level falls below the programmed value and the
port is selected via the UTOPIA PHY address, the TXCLAV signal is activated, allowing
another data transfer for that port. If this transfer exceeds the predefined buffer filling
level, the UTOPIA interface immediately enters backpressure state for this port.
When using the port specific backpressure mechanism (“p_thr_m” = 01_B or 10_B) the
general threshold defined in the “Threshold Register” (“thrshld”, see Chapter 7.33)
should be higher than the port specific threshold defined in the “Threshold Port Register”
(“thrspN”, see Chapter 7.38 to Chapter 7.41).
5.2.3 Sideband Signals of the UTOPIA Interface
In UTOPIA level 1 mode or UTOPIA level 2 single PHY mode, the framer port number
("port_nr[2:0]") can be transmitted via the UTOPIA interface. The field contains the
number of the physical (framer) port associated with that ATM cell. Its location inside the
ATM header is configurable via the “mapping_mode” bits in “utconf” (Chapter 7.34).
Possible locations are: GFC[3:1], VPI[7:5], VCI[15:13], VCI[7:5] or UDF[2:0].
In AAL mode, the channel number ("channel_nr", first timeslot number of a channel,
reference timeslot) has to be transmitted on the UTOPIA transmit interface via VCI[4:0].
If no discarding of cells with uncorrectable HEC error is selected on a specific port via
bits “a_hec_mode” in the register “acfg” (Chapter 7.2) and "p_cell_disc" in the register
"pcfN" (Chapter 7.1) an HEC error flag (HEF) indicates corrupted HEC by setting the
most significant bit in the user defined octet at the UTOPIA interface.
The bit ENB, bit 5 of the user defined octet, is responsible for the decision if cell
discarding shall base on CLP or CLPI.
Data Sheet
109
2002-05-06