mt90502ag2 Zarlink Semiconductor, mt90502ag2 Datasheet - Page 28

• Manufacturer Part Number: mt90502ag2
• Description: Multi-channel Aal2 Sar
• Manufacturer: Zarlink Semiconductor

Each entry in TX CAM is one of the following four types:
1. The TSST in that entry carries PCM or ADPCM data. An xxPCM Channel Number should be assigned.
2. The TSST in that entry belongs to an HDLC stream. An HDLC Stream Number should be assigned.
3. The TSST in that entry is a loopback channel. A Low-Latency Loopback (LLL) Channel Number should be
4. The TSST in that entry is a phasing channel. The device will use the data on that TSST to synchronize its inter-
Each TSST that carries PCM, ADPCM or HDLC data needs a CPS-Packet assembly structure in TX TDM Control
memory to have CPS-Packets assembled. The xxPCM channel number and HDLC Stream Number are used to
indicate the memory location of the CPS-Packet assembly structure and the CPS-Packet final assembly structure.
2.2.1
A low-latency loopback (LLL) is a connection between any TX TDM channel and any RX TDM channel. Up to 128
loopback connections can be established.
Channels designated as LLL channels in the TX CAM are written directly into the appropriate location in the LLL
memory of the RX TDM module. Once there, they are routed out to TSSTs that are assigned the same LLL channel
numbers in RX CAM.
2.2.2
PCM and ADPCM data is accumulated in a CPS-Packet circular buffer in TX SSRAM until the number of bytes
pending equals the length of the AAL2 CPS-Packet to be assembled, as specified in the number of EDUs (# EDU)
field of the PCM/ADPCM CPS-Packet assembly structure for that xxPCM channel. The TX TDM is capable of
treating PCM at 64 kbps and compressed ADPCM at 40, 32, 24, or 16 kbps. For the compressed ADPCM
channels, instead of capturing all 8-bits in an incoming TDM byte, the MT90502 will only sample 5-, 4-, 3-, or 2-bits
of the byte, according to the data rate. The MT90502 can be configured to sample either the MSBs or the LSBs of
TDM bytes; the configuration applies to all compressed channels.
assigned.
nal phase/sub-phase operation.
Low-Latency Loopback Channels
Treatment of PCM/ADPCM Data
Zarlink Semiconductor Inc.
MT90502
28
Data Sheet