Specifications

Saturn Debug Stub Functions 10-11
Psy-Q Development System
Assembly Language Facilities
The adapter firmware provides some useful functions which can be accessed from the
SH2 cpus via TrapA calls. These functions allow user software to interact with the
adapter downloader firmware and to change the configuration of the adapter
firmware.
Also, there are a few duplicate functions accessed via the 68000 LineA interface, that
is, 68000 instructions with opcodes $Axxx. In most cases, the default configuration
is adequate and programmers will mainly be interested in the Poll Host calls (TrapA
#$21 and dc.w $A000).
TrapA calls The following functions are currently supported on the SH2s:-
TrapA #$21 - Poll the Host PC.
TrapA #$22 - Soft Re-Entry to firmware downloader program.
This has the effect of stopping execution of the user program at the next instruction
after the TrapA. Control is returned to the adapter downloader firmware which will
sit idle, awaiting commands from the host. This allows insertion of temporary pause
points so that results can be examined in the Debugger; simply pressing the run
button allows the program to continue from that point.
Opcodes The following functions are currently supported on the 68000:-
Opcode $A000 - Poll the Host PC.
Opcode $A003 - Soft Re-Entry to firmware downloader program.