Analog Devices VISUALDSP++ 3.5, Manual

Page: 119 / 166

Vi+ Loader Manual 4-9
for 16-Bit Processors
ADSP-2192-12 DSP Loader
Using Overlay Symbols
The loader utility, when running, searches for the
OvlPciAdrTbl
and
OvlMgrTbl
symbols. If the loader cannot resolve the two symbols, it sets
both values to zero. You must declare one or both symbols in the assembly
source file to make the run-time loader handle the overlay properly.
The
OvlPciAdrTbl
symbol holds the start address of the overlay live
address table. The loader gets this symbol’s value from the input
.DXE
file
and places it in the “offset” of the first
relocation_type
array. The value
of the “offset” of the second
relocation_type
array is then the value of
the first
relocation_type
“offset” plus 2.
Consequently, each subsequent “offset” gets a value equal to the previous
“offset” plus 2. The run-time loader determines the exact the overlay live
address of each overlay according to the provided “offset” value.
Instead of defining
OvlPciAdrTbl
, define
OvlMgrTbl
in the assembly
source code. This symbol should contain the start address of the overlay
table, and the overlay table can be declared and defined in your assembly
source code. The loader gets this symbol’s value and makes the
#define
statement along with the other
#define
statement; for example:
#define CORE0_OVL_MGR_TBL 0
#define CORE0_OVL_COUNT 3
The first
#define
statement provides the start address of the overlay table.
This is zero when the loader fails to find the symbol in the input
.DXE
file.
Correct the value by manually changing the value or by defining it in the
assembly source code and re-building the loader file.
The second
#define
statement provides the number of overlay for core 0.
The run-time loader later uses the provided overlay table start address to
find the entry for the live start address each overlay and changes it before
loading the overlay table into DSP memory.