The IOM-2 bus is a synchronous full duplex communication link for interconnecting telecommunications ICs. It satisfies the requirements of ISDN and analog applications and has been defined by four major European telephone equipment manufacturers. This document provides notes on using Analog Devices' DSP, audio, and video components with the ADSP-21xx interface to the IOM-2 bus.
This document, Engineer To Engineer Note EE-36, provides technical guidance on interfacing the Analog Devices ADSP-21xx Digital Signal Processor (DSP) with the IOM Revision 2 (IOM-2) standard serial bus. The IOM-2 standard defines a synchronous full-duplex communication link designed for interconnecting telecommunications ICs, supporting both line card and terminal modes for ISDN and analog applications.
The note details the configuration of the ADSP-21xx Serial Port (SPORT) to handle time-multiplexed data streams. It covers the use of autobuffering to manage data transfer between the SPORT and internal memory, reducing interrupt overhead. Specific instructions are provided for setting up the DSP in Line Card Mode (handling 8 channels of 32 bits) and Terminal Mode (handling 24 or 32 time slots), including register settings for word length (SLEN), data type (DTYPE), and multichannel word select (MCWS). The document also includes assembly language examples for handling nibble data in terminal mode without additional glue logic.
| Data Rate | 768kbit/s (Terminal Mode) |
|---|---|
| Bus Type | Synchronous full duplex |
| Interface Wires | Four-wire serial interface |
| Max ISDN Transceivers | 8 |
| Max Codecs/Filters | 16 |
The IOM-2 bus is an industry standard serial bus for interconnecting telecommunications ICs, defined by four major European telephone equipment manufacturers.
The ADSP-21xx does not have a double serial clock feature, so the IOM-2 Data Clock (DCL) must be divided using a Flip Flop.
Autobuffering automatically transfers SPORT data to/from the internal memory of the DSP to avoid generating an interrupt after every single word.
Yes, the autobuffering mode could also be combined with the multichannel mode to handle time-multiplexed data streams.