Data Memory Space; Y Data Memory Space - Motorola DSP56309 User Manual

Memory Configuration
Memory Spaces
DSP56309 to feed two operands to the Data ALU simultaneously, enabling it to perform
a multiply-accumulate operation in one clock cycle.
X and Y data memory are identical in structure and functionality except for the upper
128 words of each space. The upper 128 words of X data memory are reserved for
internal I/O. We recommend that the programmer reserve the upper 128 words of Y
data memory for external I/O. (For further information, see Section 3.1.2.1 X Data
Memory Space and Section 3.1.2.2 Y Data Memory Space.)
X and Y data memory space each consist of the following:
¥ Internal data memory (X data RAM and Y data RAM, the default size of each is
7K, but they can be switched to 5K each)
¥ (Optionally) Off-chip memory expansion (up to 16 M in the 24-bit address mode
and 64K in the 16-bit address mode)
3.1.2.1 X Data Memory Space
The on-chip peripheral registers and some of the DSP56309 core registers occupy the top
128 locations of X data memory ($FFFF80Ð$FFFFFF in the 24-bit Address mode or
$FF80Ð$FFFF in the 16-bit Address mode). This area is called X-I/O space, and it can be
accessed by MOVE and MOVEP instructions and by bit oriented instructions (BCHG,
BCLR, BSET, BTST, BRCLR, BRSET, BSCLR, BSSET, JCLR, JSET, JSCLR, and JSSET). For
a listing of the contents of this area, see the programming sheets in
Appendix DÑProgramming Reference.
The X memory space at locations $FF0000 to $FFEFFF is reserved and should not be
accessed by the programmer.
3.1.2.2

Y Data Memory Space

The off-chip peripheral registers should be mapped into the top 128 locations of Y data
memory ($FFFF80Ð$FFFFFF in the 24-bit address mode or $FF80Ð$FFFF in the 16-bit
address mode) to take advantage of the move peripheral data (MOVEP) instruction and
the bit oriented instructions (BCHG, BCLR, BSET, BTST, BRCLR, BRSET, BSCLR, BSSET,
JCLR, JSET, JSCLR, and JSSET).
The Y memory space at locations $FF0000 to $FFEFFF is reserved and should not be
accessed by the programmer.
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