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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

DSP56002 OPERATING MODES

Table 3-3 Organization of EPROM Data Contents

Address of External

Contents Loaded to Internal

Byte-Wide Memory:

Program RAM at:

 

 

 

 

 

 

P:$C000

P:$0000

low byte

 

 

 

P:$C001

P:$0000

mid byte

 

 

 

P:$C002

P:$0000

high byte

 

 

 

•

•

 

 

 

 

•

•

 

 

 

 

•

•

 

 

 

 

P:$C5FD

P:$01FF

low byte

 

 

 

P:$C5FE

P:$01FF

mid byte

 

 

 

P:$C5FF

P:$01FF

high byte

 

 

 

After loading the internal memory, the DSP switches to the single-chip mode (Mode 0) and begins program execution at on-chip program memory location $0000.

If the user selects Mode 1 through hardware (MODA, MODB, MODC pins), the following actions occur once the processor comes out of the reset state.

1.The control logic maps the bootstrap ROM into the internal DSP program memory space starting at location $0000.

2.The control logic causes program reads to come from the bootstrap ROM (only address bits 5–0 are significant) and all writes go to the program RAM (all address bits are significant). This condition allows the bootstrap program to load the user program from $0000–$01FF.

3.Program execution begins at location $0000 in the bootstrap ROM. The bootstrap ROM program loads program RAM from the external byte-wide EPROM starting at P:$C000.

4.The bootstrap ROM program ends the bootstrap operation and begins executing the user program. The processor enters Mode 0 by writing to the OMR. This action is timed to remove the bootstrap ROM from the program memory map and re-enable read/write access to the program RAM. The change to Mode 0 is timed to allow the bootstrap program to execute a single-cycle instruction (clear status register), then a JMP #<00, and begin execution of the user program at location $0000.

3 - 10 MEMORY MODULES AND OPERATING MODES MOTOROLA

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

DSP56002 OPERATING MODES

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 described 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 bootstrap program overlays the interrupt vectors.

3.4.3Normal Expanded Mode (Mode 2)

In this mode, the internal program RAM is enabled and the hardware reset vectors to location $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).

3.4.4Development Mode (Mode 3)

In this mode, the internal program RAM is disabled and the hardware reset vectors to location $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.

3.4.5Reserved (Mode 4)

This mode is reserved for future definition. If selected, it defaults to Mode 5.

3.4.6Bootstrap 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.

MOTOROLA MEMORY MODULES AND OPERATING MODES 3 - 11

For More Information On This Product, Go to: www.freescale.com

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