Bootstrap Program - Motorola DSP56305 User Manual

4.3

BOOTSTRAP PROGRAM

The bootstrap program is factory-programmed in an internal 192 word by 24-bit
bootstrap ROM located in Program memory space at locations $FF0000–$FF00BF. The
bootstrap program can load any Program RAM segment from an external DSP56305
port. The bootstrap material described here, and listed in Appendix A, is a default,
which may be modified or replaced by the customer.
On exiting the Reset state, the DSP56305
1. samples the MODA, MODB, MODC and MODD signal lines, to determine the
reset vector location, and
2. loads their values into bits MA, MB, MC, and MD in the OMR
The contents of the MA, MB, MC, and MD bits determine which bootstrap mode the
DSP56305 enters.
1. If MA, MB, MC, and MD are all cleared (Bootstrap mode 0), the program bypasses
the bootstrap ROM and the DSP56305 starts loading instructions from external
program memory location $C00000.
2. If MA, MB, and MC are cleared and MD is set (Bootstrap mode 8), the program
bypasses the bootstrap ROM and the DSP56305 starts loading in instruction
values from external program memory location $008000.
3. Otherwise, the DSP56305 jumps to the bootstrap program entry point at $FF0000.
If the bootstrap program is loading via the Host Interface (HI32), setting the HF0 bit in
the HSR causes the DSP56305 to stop loading and begin execution of the loaded program
at the specified start address.
See Table 4-1 for a tabular description of the mode bit settings for the operating modes.
The bootstrap program options (except modes 0 and 8) can be invoked at any time by
setting the appropriate MA, MB, MC, and MD bits in the OMR and jumping to the
bootstrap program entry point, $FF0000. The mode selection bits in the OMR can be set
directly by software.
Bootstrap modes 0 and 8 are the normal functioning modes for the DSP56305. The other
bootstrap modes are bootstrap modes proper.
MOTOROLA DSP56305 User's Manual
Core Configuration
Bootstrap Program
4-5