PXB4219E Datasheet, PDF (109/290 Pages) Infineon Technologies AG – Interworking Element for 8 E1/T1 Lines

IWE8, V3.4
PXB 4219E, PXB 4220E, PXB 4221E
Interface Description
5.3
IMA Interface
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[2:0].
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 Chapter 7.24). At the same time the Port Number, where the cell came from, will be
available at pins PN[2:0].
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.
CLOCK
0
1
2
3
4
5
6
7
8
9
10 11
ATBTC
UNCHEC
PN0..2
Imai
Figure 31 IMA Interface Protocol
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
109
2003-01-20