pxb4219 Infineon Technologies Corporation, pxb4219 Datasheet - Page 111

• Manufacturer Part Number: pxb4219
• Description: Iwe8 Interworking Element For 8 E1/t1 Lines
• Manufacturer: Infineon Technologies Corporation

5.3
The IWE8 has provisions to support the Inverse Multiplexing over ATM (IMA) protocol
implemented in an external component. These are:
• An IMA interface
• A programmable threshold between read and write pointer of the mapping buffer.
If an Uncorrectable HEC Error (UNCHEC) is detected, the cell is discarded and the
UNCHEC signal will be asserted. At the same time the port number, where the cell came
from, will be available at pins PN[0:2].
The ATM Transmit Buffer Threshold Crossing (ATBTC) signal becomes active when the
difference between write and read pointer of the ATM Transmit Buffer becomes smaller
than the threshold selected with bits “bufthr” in the “Operation Mode Register” (“opmo”,
see
available at pins PN[0:2].
At the IMA interface the IWE8 operates in cycles of 12 system clocks. ATBTC can
become active during cycle #3, the UNCHEC can become active during cycle #9. The
Port number is always active for 6 cycles.
Figure 31
For more detailed information on the IMA interface refer to the Application Hint “Inverse
Multiplexing for ATM (IMA) with the Interworking Element IWE8”.
Data Sheet
Chapter
CLOCK
ATBTC
UNCHEC
PN0..2
IMA Interface
7.24). At the same time the Port Number, where the cell came from, will be
IMA Interface Protocol
0
1
2
3
4
111
5
6
PXB4219 / PXB4220 / PXB4221
7
8
9
Interface Description
10
11
2002-05-06