PSB50505EV13GXT Lantiq, PSB50505EV13GXT Datasheet - Page 43

• Manufacturer Part Number: PSB50505EV13GXT
• Manufacturer: Lantiq

Specifications of PSB50505EV13GXT

• Lead Free Status / RoHS Status: Supplier Unconfirmed

pressure state. This results in two side effects, which have to be taken into account for
the calculation of threshold values.
• After back pressure state has been entered, up to 8 additional cells may be transferred
• Before a certain cell can cause port specific back pressure, it has to traverse the
4.1.1.2
The discarding of cells is available for ATM ports. It can depend on
• Buffer filling level and CLP (Bit 0 of the 4th ATM header octet)
• Buffer filling level and CLPI (Cell Loss Priority Internal, bit 6 of the UDF octet at the
The bit ENB, bit 5 of the UDF octet at the UTOPIA interface, is responsible for the
decision if discarding shall base on CLP or CLPI. For bit locations see
The buffer threshold for discarding cells is configured by register “thrshld” and applies to
all ports.
Cells that are going to be extracted via the microprocessor interface will be ignored by
the cell discard mechanism
Table 12
ENB
0
0
1
1
4.1.1.3
When the ATM Transmit Buffer of a port is empty, idle or unassigned cells are
transmitted to provide cell rate de-coupling.
Idle cells are transmitted as defined in the ITU-T I.361 [30]. Unassigned cells can be
inserted, as defined in the B-ISDN UNI and NNI physical layer generic criteria [15].
The 4 MSBs of header octet 1 and the 4 LSBs of header octet 4 are programmable in
the “prg_tx_hd” field of the TX Idle/Unassigned Cell Control Register (txid, see
Chapter
Data Sheet
from the UTOPIA input buffer to the port buffer.
UTOPIA input buffer, resulting in a delay of 4.2 to 16.8 µs.
UTOPIA interface)
7.10). All other header bits will be 0.
CLPI
x
x
0
1
Cell Discarding
Cell rate de-coupling: Idle/Unassigned Cell Insertion
ATM Cell Discarding
CLP
0
1
x
x
Discarding
No
Yes, if buffer threshold has been exceeded
No
Yes, if buffer threshold has been exceeded
43
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
Figure
IWE8, V3.4
2003-01-20
30.