Jameco Electronics Rabbit 3000 - Manual (Page 135)

126 Rabbit 3000 Microprocessor
Figure 8-6. Use of Physical Memory Separate I & D Space Model
In Figure 8-6 arrows indicate the direction in which variables and constants are allocated
as the compile or assemble proceeds. Each of these arrows starts at a constant location in
physical memory. This is important because the Dynamic C debugging monitor needs to
keep a small number of constants and variable in data space and it needs to be able to
access these regardless of the state of the user program. The Dynamic C debugger vari-
ables are kept at the top of the data segment starting at 52k and working down in memory.
The user-program variables are allocated by the compiler starting just below the Dynamic
C debugger data. The Dynamic C constants start at address zero. User constants are allo-
cated stating at a low address just above the Dynamic C constants.
0k
52k
Root
I Space
64k
Constant
D Space
512k
512k+52k
64k+4*n
512k+4*n
Variable
D Space
1024k
Flash memory available
for extended code, constant
data. Ram memory available.
alloc consts allocate vars
alloc xdata vars
alloc xcode
xconsts