Bootstrap Program - Motorola DSP56303 User Manual

Bootstrap Program

Table 4-1. DSP56303 Operating Modes (Continued)
Mode MODD MODC
F 1 1
4.2 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 byte-wide EPROM, the SCI,
or the host port. The bootstrap program code is listed in Appendix A.
Upon exit from the Reset state, the DSP56303 samples the
their values into OMR[MA–MD]. The mode input signals (
MA, MB, MC, and MD bits determine which bootstrap mode the DSP56303 enters (see
Table 4-1).
Note: To stop the bootstrap in any HI08 bootstrap mode, set the Host Flag 0 (HF0). The
loaded user program begins executing from the specified starting address.
You can invoke the bootstrap program options (except modes 0 and 8) at any time by writing
the appropriate values to the MA, MB, MC, and MD bits in the OMR and jumping to the
bootstrap program entry point, $FF0000. Software can set the mode selection bits directly in
the OMR. Bootstrap modes 0 and 8 are the normal DSP56303 functioning modes. The other
bootstrap modes select different specific bootstrap loading source devices. Refer to Appendix
A for detailed information about the bootstrap program.
4-8
Reset
MODB MODA
Vector
1 1 $FF0000
DSP56303 User's Manual
Description
HI08 bootstrap in MC68302 bus mode
The bootstrap program loads the program RAM from
the Host Interface programmed to operate in the
MC68302 bus mode, in single-strobe pin
configuration. The HOST MC68302 bootstrap code
expects accesses that are byte wide. The HOST
MC68302 bootstrap code expects to read 3 bytes
forming a 24-bit word specifying the number of
program words, 3 bytes forming a 24-bit word
specifying the address to start loading the program
words and then 3 bytes forming 24-bit words for each
program word to be loaded. The program words are
stored in contiguous PRAM memory locations
starting at the specified starting address. After
reading the program words, program execution starts
from the same address where loading started. The
Host Interface bootstrap load program may be
stopped by setting the Host Flag 0 (HF0). This starts
execution of the loaded program from the specified
starting address.
– signal lines and loads
MODA MODD
– ) and the resulting
MODA MODD