DSP56002 OPERATING MODES
MOTOROLA
MEMORY MODULES AND OPERATING MODES
3 - 11
The user can also get into the bootstrap mode (Mode 1) through software by writing zero
to MC and MB, and one to MA in the OMR. This selection initiates a timed operation to
map the bootstrap ROM into the program address space (after a delay to allow execution
of a single-cycle instruction), and then a JMP #<00 to begin the bootstrap process de-
scribed previously in steps 1 through 4. This technique allows the user to reboot the
system (with a different program, if desired).
The code to enter the bootstrap mode is as follows:
MOVEP
#0,X:$FFFF
;Disable interrupts.
MOVEC
#1,OMR
;The bootstrap ROM is mapped
;into the lowest 64 locations
;in program memory.
NOP
;Allow one cycle delay for the
;remapping.
JMP
<$0
;Begin bootstrap.
The code disables interrupts before executing the bootstrap code. Otherwise, an interrupt
could cause the DSP to execute the bootstrap code out of sequence because the boot-
strap program overlays the interrupt vectors.
3.4.3
Normal Expanded Mode (Mode 2)
In this mode, the internal program RAM is enabled and the hardware reset vectors to lo-
cation $E000. (The memory maps for Mode 0 and Mode 2 are identical. The difference
for Mode 0 is that, after reset, the instruction at location $E000 is executed instead of the
instruction at $0000 — see Figure 3-1 and Table 3-2).
3.4.4
Development Mode (Mode 3)
In this mode, the internal program RAM is disabled and the hardware reset vectors to lo-
cation $0000. All references to program memory space are directed to external program
memory. The reset vector points to location $0000. The memory map for this mode is
shown in Figure 3-1 and Table 3-2.
3.4.5
Reserved (Mode 4)
This mode is reserved for future definition. If selected, it defaults to Mode 5.
3.4.6
Bootstrap From Host (Mode 5)
In this mode, the Bootstrap ROM is enabled and the bootstrap program is executed. This is
similar to Mode 1 except that the bootstrap program loads internal P: RAM from the Host Port.
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..