This document provides technical notes on using Analog Devices' DSP components and development tools, including the two major configuration modes of the ADSP-218x DSPs: full memory mode and host memory mode.
This document describes two major configurations for the external busses on the ADSP-218x DSPs: Full Memory Mode and Host Mode. Full Memory Mode provides complete use of the external address and data busses, allowing BDMA operation with full external overlay memory and I/O capability, while disabling IDMA functionality. In contrast, Host Mode allows complete IDMA port operation but limits external addressing capabilities by repurposing lower address and data bus pins for IDMA control.
| External Data Bus Width | 24 bit |
|---|---|
| External Address Bus Width | 14 bit |
| Memory Select Signals | 5 |
| Supported Models | 2184, 2184L, 2185, 2185L, 2185M, 2186, 2186L, 2186M, 2187L, 2188M, 2189M |
The operating modes are determined by the state of the Mode C pin during /RESET and cannot be changed once the DSP is powered up.
No, IDMA functionality is disabled in Full Memory Mode.
In Host Mode, the lower eight bits of the data bus, D[7:0], become IDMA control pins and IAD bus pins.