PXB4219E Datasheet, PDF (84/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Operational Description
4.10
Cell Extraction
Cells coming in downstream direction from the UTOPIA Transmit Interface can be
extracted to the Cell Extraction Buffer instead of the Reassembly/ATM Transmit Buffer.
The Cell Extraction Buffer offers space for 254 ATM cells. It is located in the external
RAM.
Incoming cells are written to the Extraction Buffer if
• their VCI matches to a pattern predefined in the Cell Filter VCI Pattern 1 Register
(cfvp1, see Chapter 7.26) where each bit of the VCI can be masked via the Cell Filter
VCI Mask Register 1 (cfvm1, Chapter 7.27)
• or their VCI matches to a pattern predefined in the Cell Filter VCI Pattern 2 Register
(cfvp2, see Chapter 7.28) where each bit of the VCI can be masked via the Cell Filter
VCI Mask Register 1 (cfvm1, Chapter 7.29)
• or their PTI matches to one of two pattern defined in the Cell Filter Payload Type
Register (“cfpt”, see Chapter 7.30) each of these patterns can also be masked via
“cfpt”.
Once a cell has been extracted to the cell Extraction Buffer, it is indicated by the bit
“cf_fifo_n_empty” in the Extended Interrupt Status Register (“eis1”, see Chapter 7.19).
Cells can be read with the help of the read pointer (“rdptr”) in the Cell Filter Read Pointer
Register (“cfrp”, Chapter 7.32). The rdptr can have values between 02_H and FF_H. This
value is a pointer to the current base-address, at which the microprocessor can read the
next extracted cell from the Extraction Buffer.
MPADR = 26000_H + 20_H · rdptr
[13]
RMADR = 03000_H + 10_H · rdptr
[14]
After reading the cell the rdptr has to be incremented by the microprocessor and written
back. If the rdptr is incremented to its maximum value FF_H the value 02_H has to be
written back instead.
Data Sheet
84
2003-01-20