Memory Spaces; Program Memory Space; Data Memory Spaces - Motorola DSP56309 User Manual

3.1

MEMORY SPACES

The DSP56309 provides three independent memory spaces:
¥ Program
¥ X data
¥ Y data
Each memory space uses 24-bit addressing by default. The program and data word
length is 24 bits. Moreover, this device supports remapping address attribute registers
Òon the fly,Ó thus allowing access to 16 M of memory.
The DSP56309 provides a sixteen-bit compatibility mode that effectively uses 16-bit
addressing for each memory space, allowing access to 64K each of memory. This mode
puts zeroes in the most significant byte of the usual (24-bit) program and data word; it
ignores the zeroed byte, thus effectively using 16-bit program and data words. The
sixteen-bit compatibility mode allows the DSP56309 to use 56000 object code without
change, thus minimizing system cost for applications that use the smaller address space.
See the DSP56300 Family Manual for further information.
3.1.1

Program Memory Space

Program memory space consists of the following:
¥ Internal program memory (Program RAM, 20K by default)
¥ Bootstrap Program ROM (192 x 24-bit)
¥ (Optionally) off-chip memory expansion (as much as 16 M in 24-bit mode and
64K in 16-bit mode)
¥ (Optionally) instruction cache (1K) formed from Program RAM
Program memory space at locations $FF00C0 to $FFFFFF is reserved and should not be
accessed.
3.1.2

Data Memory Spaces

Data memory space is divided into X data memory and Y data memory to match the
natural partitioning of DSP algorithms. The data memory partitioning allows the
MOTOROLA DSP56309UM/D
Memory Configuration
Memory Spaces
3-3