Memory Management Using Overlays - Analog Devices VisualDSP++ 3.5 Manual

Memory Management Using Overlays

Memory Management Using Overlays
To reduce DSP system costs, many applications employ processors with
small amounts of on-chip memory and place much of the program code
and data off-chip. The linker supports the linking of executables for sys-
tems with overlay memory. Applications notes on the Analog Devices
Web site provide detailed descriptions of this technique; for example,
• AN 572 "Overlay Linking on the ADSP-219x"
• EE-152 "Using Software Overlays with the ADSP-219x and
VisualDSP 2.0++"
• EE-100 "ADSP-218x External Overlay Memory"
This section describes the use of memory overlays with 16-bit DSPs. The
topics are:
• "Introduction to Memory Overlays" on page 5-5
• "Overlay Managers" on page 5-7
• "Memory Overlay Support" on page 5-8
• "Example – Managing Two Overlays" on page 5-12
• "Linker-Generated Constants" on page 5-15
• "Overlay Word Sizes" on page 5-15
• "Storing Overlay ID" on page 5-16
• "Overlay Manager Function Summary" on page 5-17
• "Reducing Overlay Manager Overhead" on page 5-17
• "Using PLIT{} and Overlay Manager" on page 5-22
5-4 VisualDSP++ 3.5 Linker and Utilities Manual
for 16-Bit Processors