MT90500 Mitel Semiconductor, MT90500 Datasheet - Page 155

• Manufacturer Part Number: MT90500
• Description: Multi-Channel ATM AAL1 SAR
• Manufacturer: Mitel Semiconductor

The input channel is now automatically written to the shared buffer, and the output channel is automatically
read from the shared buffer, resulting in the input channel being written to the output channel. The throughput
delay in this setup is 1 msec. This is due to the 4-frame TDM Input Frame Buffer followed by the 4-frame TDM
Output Frame Buffer.
7.6.3
The MT90500 can be used in trunking applications. In trunking applications it is often desirable to maintain an
ATM VC of constant bandwidth (constant Nx64) but to re-map the TDM channels within the ATM VC to different
TDM channels on the backplane or TDM trunks.
Given an established VC, and the need to shut down a TDM channel and re-use the bandwidth within the VC,
re-mapping a TDM channel can be done on the MT90500 as follows:
1) Tristate the output TDM channel at the reassembly device (receive TDM end), using the OE
Registers, to end the old TDM channel connection.
2) Re-write the TDM-channel-to-TX-Circular-Buffer mapping in the Transmit Circular Buffer Control
Structure at the segmentation device (transmit end). This is done by writing a new time slot and/or
stream into the word-entry associated with the particular TX circular buffer.
3) Re-write the RX-Circular-Buffer-to-TDM-channel mapping in the External Memory to Internal
Memory Control Structure at the reassembly device (receive TDM end). This is done by writing a new
TDM Channel # into the first word of the two-word-entry associated with the particular RX circular
buffer.
4) Turn on the output TDM channel at the reassembly device (receive TDM end), using the OE
Registers, to start the new connection.
Circular Buffers
(Receive AND Transmit programmed into same addresses)
DS0 Trunking, or Dynamic TDM channel re-mapping
Circular
Buffer
(64 bytes)
Circular
Buffer
(
Circular
Buffer
(64 bytes)
64 bytes)
Figure 72 - TDM-to-TDM Loopback/Switching
TDM
Output Frame
Buffer
TDM
Input Frame
Buffer
Output TDM Channels
Input TDM Channels
MT90500
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