Motorola DSP56303 User Manual page 71

Table 4-1. DSP56303 Operating Modes (Continued)
Mode MODD MODC
7 0 1
8 1 0
9 1 0
Reset
MODB MODA
Vector
1 1 $FF0000
0 0 $008000
0 1 $FF0000
Core Configuration
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.
Expanded mode
Bypasses the bootstrap ROM, and the DSP56303
starts fetching instructions beginning at address
$008000. Memory accesses are performed using
SRAM memory access type with 31 wait states and
no address attributes selected.
Bootstrap from byte-wide memory
The bootstrap program it loads a program RAM
segment from consecutive byte-wide P memory
locations, starting at P:$D00000 (bits 7-0). The
memory is selected by the Address Attribute AA1
and is accessed with 31 wait states. The EPROM
bootstrap code expects to read 3 bytes specifying
the number of program words, 3 bytes specifying the
address to start loading the program words and then
3 bytes for each program word to be loaded. The
number of words, the starting address and the
program words are read least significant byte first
followed by the mid and then by the most significant
byte. The program words are condensed into 24-bit
words and 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.
Operating Modes
4-5