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;;; 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 = sp
;;; A6 = emulated PC XXX
;;; A5 = instruction table base pointer
;;; A4 = emulated SP XXX
;;; A3 = pointer to flag_storage
;;; A2 =
;;; A1 =
;;; A0 =
;;;
;;; D0 = current instruction, scratch for macros
;;; D1 = scratch for instructions
;;; D2 = undefined
;;;
;;;
;;; The following have their shadows in the top half of the register
;;; D3 = AF A is in the low byte, F in the high byte (yeah ... speed)
;;; D4 = BC B high, C low
;;; D5 = DE D high, E low
;;; D6 = 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 = IX (hi), IY (low)
;;; Assemble with the following flags:
;;; a68k -l -n -g -t main.asm
;;; -n is important, it disables optimizations
;;; emulated I and R are both in RAM
xdef _ti89
; xdef _ti92plus
xdef __main
xdef _tigcc_native
include "../tios.h"
__main:
movem.l d0-d7/a0-a6,-(sp)
bsr emu_setup
lea emu_plain_op,a5
bsr emu_run
movem.l (sp)+,d0-d7/a0-a6
rts
include "ports.asm"
include "interrupts.asm"
include "flags.asm"
include "alu.asm"
emu_setup:
;; Allocate memory pages; for now I assume this succeeds
move.l #$4000,-(a7)
ROM_CALL malloc
addq #4,a7
move.l a0,ref_0
move.l #$4000,-(a7)
ROM_CALL malloc
addq #4,a7
move.l a0,ref_1
move.l #$4000,-(a7)
ROM_CALL malloc
addq #4,a7
move.l a0,ref_2
move.l #$4000,-(a7)
ROM_CALL malloc
addq #4,a7
move.l a0,ref_3
movea emu_plain_op,a5
lea emu_run,a2
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:
move.w d1,d0
andi.w #$3FFF,d0
movea.w d0,a0
move.w d1,d0
andi.w #$C000,d0 ; Can cut this out by pre-masking the table.
rol.w #2,d0
adda.l deref_table(pc,d0.w),a0
rts
deref_table:
ref_0: dc.l 0 ; bank 0
ref_1: dc.l 0 ; bank 1
ref_2: dc.l 0 ; bank 2
ref_3: dc.l 0 ; bank 3
;; 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.
underef:
lea deref_table(pc),a1
move.l a0,d0
sub.l (a1)+,d0
bmi.s underef_not0
cmpi.l #$4000,d0
bmi.s underef_thatsit
underef_not0:
move.l a0,d0
sub.l (a1)+,d0
bmi.s underef_not1
cmpi.l #$4000,d0
bmi.s underef_thatsit
underef_not1:
move.l a0,d0
sub.l (a1)+,d0
bmi.s underef_not2
cmpi.l #$4000,d0
bmi.s underef_thatsit
underef_not2:
suba.l (a1)+,a0
;; if that fails too, well shit man!
underef_thatsit:
rts
;; =========================================================================
;; instruction instruction instruction ================================
;; _ _ _ _ ================================
;; __| (_)___ _ __ __ _| |_ ___| |__ ================================
;; / _` | / __| '_ \ / _` | __/ __| '_ \ ================================
;; | (_| | \__ \ |_) | (_| | || (__| | | | ================================
;; \__,_|_|___/ .__/ \__,_|\__\___|_| |_| ================================
;; |_| =================================
;; ========== ========================================================
;; =========================================================================
include "opcodes.asm"
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
|
