Memory Spaces; Program Memory Space - Motorola DSP56305 User Manual

3.1

MEMORY SPACES

The DSP56305 provides three independent memory spaces:
• Program
• X data
• Y data
Each memory space uses (by default) twenty-four external address lines for addressing,
allowing access to 16 M of external memory. Program and data word length is 24 bits,
and internal memory uses 24-bit addressing.
The DSP56305 provides a Sixteen-bit Compatibility mode that effectively uses 16-bit
addressing for each memory space, allowing access to 64 K each of memory. This mode
puts 0s in the most significant byte of the usual (24-bit) program and data word, and
ignores the zeroed byte, thus effectively using 16-bit program and data words. The
Sixteen-bit Compatibility mode allows the DSP56305 to use 56000 object code without
change (thus minimizing system cost for applications that use the smaller address
space). See the DSP56300 Family Manual, Section 6.4 for further information.
Internal memory is 24-bit wide, high-speed, Static RAM occupying the lowest parts of
memory space.
3.1.1

Program Memory Space

Program memory space consists of:
• Internal program memory, consisting of:
Program RAM, 6.5 K by default
Program ROM, 6 K x 24-bit
• Bootstrap Program ROM (192 x 24-bit)
• (Optionally) Off-chip memory expansion (as much as 16 M in 24-bit mode and 64
K in Sixteen-bit Compatibility mode)
• (Optionally) Instruction Cache (1 K) formed from the uppermost Program RAM
MOTOROLA DSP56305 User's Manual
Memory Configuration
Memory Spaces
3-3