MT92220 Datasheet, PDF (82/210 Pages) Zarlink Semiconductor Inc – 1023 Channel Voice Over IP/AAL2 Processor

Data Sheet
MT92220
One of the most important characteristics of the generation of AAL2 packets is that it uses the bus timestamp to
synchronize and generate the sequence number within the UUI. This has many advantages, notably deterministic
behavior of the sequence numbers and the synchronization of different channels' sequence numbers together,
allowing completely synchronized transport of several voice channels across many AAL2 connections. The UUI
sequence number is extracted by dividing the current timestamp by the Sequence Number Interval, then
performing a modulo by the total sequence number sequence size. For example, if the Sequence Number Interval
is 40 frames and 4 sequence number bits are used, the operation is (timestamp / 40) % (2^4). These operation
must also take into account the fact that the timestamp can wrap: the Timestamp Remainder and Timestamp Wrap
Inc fields take care of that. Timestamp Wrap Inc must be programmed to: 2³² % ((Sequence Number Interval *
(2^{Num Seq Bits}).
The format of the TX AAL2 connection structure is the following:
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
+0
+2
+4
+6
TX AAL2 VC Structure Base Address [20:5]
+8
AAL2 CID [7:0]
+A
+C
+E
+10
+12
+14
Transmitted Packet Count [15:0]
+16
+18
Transmitted Octet Count [31:16]
+1A
Transmitted Octet Count [15:0]
+1C
+1E
+20
+22
+24
+26
Figure 47 - TX AAL2 Connection Structure
Zarlink Semiconductor Inc.
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