Memory Overlay Support - Analog Devices VisualDSP++ 3.5 Manual

Memory Management Using Overlays
The more important of the two symbols is the breakpoint at
Code execution in the overlay manager should pass through this location
once an overlay has been fully swapped in. At this point, the debugger
may probe the target to determine which overlays are in context. The sym-
bol manager will now set any breakpoints requested on the overlays and
resume execution.
The second breakpoint is at
defined in the overlay manager, in code always executed immediately
before the transfer of a new overlay begins. The breakpoint disables all of
the overlays in the debugger—the idea being that while the target is run-
ning in the overlay manager, the target is "unstable" in the sense that the
debugger should not rely on the overlay information it may gather since
the target is "in flux". The debugger will still function without this break-
point, but there may be some inconsistencies while overlays are being
moved in and out.

Memory Overlay Support

The overlay support provided by the DSP tools includes:
• Specification of the live and run locations of each overlay
• Generation of constants
• Redirection of overlay function calls to a jump table
Overlay support is partially user-designed in the
specify which overlays share run-time memory and which memory seg-
ments establish the live and run space.
Listing 5-1 shows the portion of an
This overlay declaration configures the two overlays to share a common
run-time memory space. The syntax for the
described in "OVERLAY_GROUP{}" on page
5-8
. The label
_ov_start
file that defines two overlays.
.LDF
OVERLAY_INPUT{}
VisualDSP++ 3.5 Linker and Utilities Manual
_ov_end
should be
_ov_start
file (LDF). You
.LDF
command is
3-33.
for 16-Bit Processors
.