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|
||| -*- mode: gas; gas-comment-char: 124 -*-
||| z80 emulator for 68k calculators
||| Astrid Smith
||| Project started: 2010-06-06
||| GPL
||| Yes, I use lots of big ascii art. With this much code, you need
||| something to catch your eye when scrolling through it. I suppose
||| I'll split it into different files later.
||| Registers used:
|||
||| A7 68000 stack pointer
||| A6/epc emulated PC
||| A5 instruction table base pointer
||| A4 emulated SP
||| A3 pointer to flag_storage
||| A2
||| A1
||| A0
|||
||| D0 current instruction, scratch for macros
||| D1 scratch for instructions
||| D2 further scratch
|||
|||
||| The following have their shadows in the top half of the register
||| D3/eaf = AF A is in the low byte, F in the high byte (yeah ... speed)
||| D4/ebc = BC B high, C low
||| D5/ede = DE D high, E low
||| D6/ehl = HL H high, L low
|||
||| IY is used more often so it's easier to get at. It can be slow
||| but I don't really care to go to the effort to make it so.
||| D7/eixy = IX (hi word), IY (low word)
||| emulated I and R are both in RAM
.xdef _ti89
|.xdef _ti92plus
.xdef __main
|.xdef _tigcc_native
.include "./tios.inc"
.include "global.inc"
__main:
movem.l d0-d7/a0-a6,-(sp)
bsr init_load
bsr display_setup
bsr emu_setup
lea emu_plain_op,a5
|| ... aaaaand we're off!
jsr emu_run
bsr emu_teardown
bsr display_teardown
bsr unload
movem.l (sp)+,d0-d7/a0-a6
rts
.include "ports.s"
.include "interrupts.s"
.include "flags.s"
.include "alu.s"
emu_setup:
movea.l emu_op_00,a5
lea emu_run,a2
lea flag_storage,a3
move.w #0x4000,d1
bsr deref
move.l a0,epc
move.l a0,esp
rts
emu_teardown:
rts
|| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|| _ __ ___ ___ _ __ ___ ___ _ __ _ _ |||||||||||||||||||||||||||
|| | '_ ` _ \ / _ \ '_ ` _ \ / _ \| '__| | | | \\\\\\\\\\\\\\\\\\\\\\\\\\\
|| | | | | | | __/ | | | | | (_) | | | |_| | |||||||||||||||||||||||||||
|| |_| |_| |_|\___|_| |_| |_|\___/|_| \__, | ///////////////////////////
|| of the virtual type |___/ |||||||||||||||||||||||||||
|| =============================================JJJJJJJJJJJJJJJJJJJJJJJJJJJ
|| Take a virtual address in d1 and dereference it. Returns the
|| host address in a0. Destroys a0, d0.
deref: | 76 cycles + 18 cycles for bsr
| 20 bytes to inline, saves 34 cycles per call
move.w d1,d0
andi.w #0x3FFF,d0
movea.w d0,a0
move.w d1,d0
andi.w #0xC000,d0 | Can cut this out by pre-masking the table.
rol.w #4,d0
adda.l deref_table(pc,d0.w),a0
rts
.even
.data
deref_table:
mem_page_0: .long 0 | bank 0 / 0x0000
mem_page_1: .long 0 | bank 1 / 0x4000
mem_page_2: .long 0 | bank 2 / 0x8000
mem_page_3: .long 0 | bank 3 / 0xc000
.xdef mem_page_0
.xdef mem_page_1
.xdef mem_page_2
.xdef mem_page_3
mem_page_loc_0: .byte 0
mem_page_loc_1: .byte 0
mem_page_loc_2: .byte 0
mem_page_loc_3: .byte 0
.xdef mem_page_loc_0
.xdef mem_page_loc_1
.xdef mem_page_loc_2
.xdef mem_page_loc_3
pages: .long 0
.xdef pages
.text
|| Take a physical address in a0 and turn it into a virtual
|| address in d0
|| Destroys d0
| XXX AFAICS, a1 is currently a scratch address register, so you can load deref_table in it, and then save some space:
| But you may wish to use it for other purposes in the future, so you needn't integrate that immediately.
|| Guessing this is 300 cycles.
underef:
move.l d2,-(a7)
lea deref_table(pc),a1
move.l a0,d0
clr.w d2
sub.l (a1)+,d0
bmi.s underef_not0
cmpi.l #0x4000,d0
bmi.s underef_thatsit
underef_not0:
move.l a0,d0
move.w #0x4000,d2
sub.l (a1)+,d0
bmi.s underef_not1
cmpi.l #0x4000,d0
bmi.s underef_thatsit
underef_not1:
move.l a0,d0
move.w #0x8000,d2
sub.l (a1)+,d0
bmi.s underef_not2
cmpi.l #0x4000,d0
bmi.s underef_thatsit
underef_not2:
move.w #0xc000,d2
suba.l (a1)+,a0
|| if that fails too, well shit man!
moveq #0,d0
underef_thatsit:
add.w d2,d0
move.l (a7)+,d2
rts
|| =========================================================================
|| instruction instruction instruction ================================
|| _ _ _ _ ================================
|| __| (_)___ _ __ __ _| |_ ___| |__ ================================
|| / _` | / __| '_ \ / _` | __/ __| '_ \ ================================
|| | (_| | \__ \ |_) | (_| | || (__| | | | ================================
|| \__,_|_|___/ .__/ \__,_|\__\___|_| |_| ================================
|| |_| =================================
|| ========== ========================================================
|| =========================================================================
.include "opcodes.s"
emu_run:
|| XXX: make this actually return
DONE
rts
emu_op_undo_cb:
emu_op_undo_dd:
emu_op_undo_ed:
emu_op_undo_fd:
rts
|
