Host Interface (Hi08) - Motorola DSP56309 User Manual

On exiting the reset state, the DSP56309 does the following:
1. Samples the MODA, MODB, MODC, and MODD signal lines.
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
DSP56309 enters:
1. If MA, MB, MC, and MD are all cleared (Bootstrap mode 0), the program bypasses
the bootstrap ROM, and the DSP56309 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 DSP56309 starts loading in instruction
values from external program memory location $008000.
3. Otherwise (Bootstrap modes 1Ð7), the DSP56309 jumps to the bootstrap program
entry point at $FF0000.
If the bootstrap program is loading via the host interface (HI08), setting the HF0 bit in
the host status register (HSR) causes the DSP56309 to stop loading and begin executing
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 MA, MB, MC, and MD bits in the OMR and jumping to the bootstrap
program entry point, $FF0000. Software can directly set the mode selection bits in the
OMR.
Bootstrap modes 0 and 8 are the normal functioning modes for the DSP56309. Bootstrap
modes 1Ð7 are the bootstrap modes proper.
Bootstrap modes 9, A, C, D, E, F select different, specific devices for loading the
bootstrap source. In those bootstrap modes, the bootstrap program expects the following
data sequence when downloading the user program through an external port:
1. Three bytes defining the number of (24-bit) program words to be loaded
2. Three bytes defining the (24-bit) start address to which the user program loads in
the DSP56309 program memory
3. The user program (three bytes for each 24-bit program word)
MOTOROLA DSP56309UM/D
Core Configuration
Bootstrap Program
4-5