mirror of
https://gitlab.com/freepascal.org/fpc/source.git
synced 2025-04-05 15:47:54 +02:00
1ae70c6825
the ZX Spectrum startup code, because the ROM handler requires the IY register to always have a specific value, but the FPC code generator uses the IY register for various purposes, which causes random crashes and glitches when the timer interrupt occurs. git-svn-id: trunk@45677 -
124 lines
2.5 KiB
ObjectPascal
124 lines
2.5 KiB
ObjectPascal
{
|
|
This file is part of the Free Pascal run time library.
|
|
Copyright (c) 2020 by Free Pascal development team
|
|
|
|
This file contains startup code for the ZX Spectrum
|
|
|
|
See the file COPYING.FPC, included in this distribution,
|
|
for details about the copyright.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
|
|
|
|
**********************************************************************}
|
|
|
|
unit si_prc;
|
|
|
|
{$SMARTLINK OFF}
|
|
|
|
interface
|
|
|
|
implementation
|
|
|
|
{$GOTO ON}
|
|
|
|
var
|
|
FPC_SAVE_IY: word; external name 'FPC_SAVE_IY';
|
|
fpc_stackarea_start: word; external name '__fpc_stackarea_start';
|
|
fpc_stackarea_end: word; external name '__fpc_stackarea_end';
|
|
|
|
procedure PascalMain; external name 'PASCALMAIN';
|
|
|
|
{ this *must* always remain the first procedure with code in this unit }
|
|
procedure _start; assembler; nostackframe; public name 'start';
|
|
label
|
|
bstart,bend,loop,loop2,our_int_handler,key_int;
|
|
asm
|
|
{ init the stack }
|
|
ld sp, offset fpc_stackarea_end
|
|
|
|
{ zero the .bss section }
|
|
ld bc, offset bstart
|
|
ld hl, offset bend
|
|
scf
|
|
ccf
|
|
sbc hl, bc
|
|
ld a, 0
|
|
loop:
|
|
ld (bc), a
|
|
inc bc
|
|
dec hl
|
|
cp a, l
|
|
jr NZ, loop
|
|
cp a, h
|
|
jr NZ, loop
|
|
|
|
{ save IY (must be done after zeroing the .bss section) }
|
|
ld (FPC_SAVE_IY), iy
|
|
|
|
{ prepare to run in interrupt mode 2; install our own interrupt handler }
|
|
di
|
|
ld de, 65024
|
|
ld hl, 65021
|
|
ld a, d
|
|
ld i, a
|
|
ld a, l
|
|
loop2:
|
|
ld (de), a
|
|
inc e
|
|
jr nz, loop2
|
|
inc d
|
|
ld (de), a
|
|
ld (hl), 195
|
|
ld hl, offset our_int_handler
|
|
ld (65022), hl
|
|
im 2
|
|
ei
|
|
|
|
{ ready to run the main program }
|
|
jp PASCALMAIN
|
|
|
|
{ replacement for the ROM interrupt handler that preserves IY and that
|
|
doesn't break if IY is changed }
|
|
our_int_handler:
|
|
push af
|
|
push hl
|
|
push iy
|
|
ld iy, (FPC_SAVE_IY)
|
|
ld hl, (23672)
|
|
inc hl
|
|
ld (23672), hl
|
|
ld a, h
|
|
or a, l
|
|
jr nz, key_int
|
|
inc (iy+64)
|
|
key_int:
|
|
push bc
|
|
push de
|
|
call 703
|
|
pop de
|
|
pop bc
|
|
ld (FPC_SAVE_IY), iy
|
|
pop iy
|
|
pop hl
|
|
pop af
|
|
ei
|
|
reti
|
|
|
|
{ When using the SDCC-SDLDZ80 linker, the first object module defines the
|
|
order of areas (sections). Since this module contains the startup code,
|
|
it is loaded first, so we define all the sections we use in the proper
|
|
order. }
|
|
area '_DATA'
|
|
area '_BSS'
|
|
bstart:
|
|
area '_BSSEND'
|
|
bend:
|
|
area '_HEAP'
|
|
area '_STACK'
|
|
area '_CODE'
|
|
end;
|
|
|
|
end.
|