Specifying The Memory Map; Memory Usage - Analog Devices VisualDSP++ 3.5 Manual

Link Target Description
The two address buses (PMA and DMA) share a single external address
bus to allow memory to be expanded off-chip, and the two data buses
(PMD and DMD) share a single external data bus. Boot memory space
and I/O memory space also share the external buses. Program memory can
store both instructions and data to enable the ADSP-2191M DSP to fetch
two operands in a single cycle, one from program memory and one from
data memory. The DSP's dual memory buses also let the ADSP-219x core
fetch an operand from data memory and the next instruction from pro-
gram memory in a single cycle.

Specifying the Memory Map

A DSP program must conform to the constraints imposed by the proces-
sor's data path (bus) widths and addressing capabilities. The following
steps show an
.LDF
memory segments that support the
"SECTIONS{}" on page
The three steps involved in allocating memory are:
• "Memory Usage" on page 2-18
• "Memory Characteristics" on page 2-20
• "Linker MEMORY{} Command in .LDF File" on page 2-24

Memory Usage

Input section names are generated automatically by the compiler or are
specified in the assembly source code. The
ment names and output section names. The default
compiler-generated input sections (refer to the "Input Section" column in
tables below). The produced
for each input section. Although programmers typically do not use output
section labels, the labels are used by downstream tools.
2-18
file for a hypothetical project. This file specifies several
SECTIONS{}
3-42.
file has a corresponding output section
.DXE
VisualDSP++ 3.5 Linker and Utilities Manual
command, as shown in
file defines memory seg-
.LDF
file handles all
.LDF
for 16-Bit Processors