diff options
Diffstat (limited to 'main.asm')
| -rw-r--r-- | main.asm | 143 |
1 files changed, 115 insertions, 28 deletions
@@ -11,17 +11,16 @@ ;;; Registers used: ;;; ;;; A7 = sp -;;; A6 = address space base pointer -;;; A5 = -;;; A4 = -;;; A3 = instruction table base pointer -;;; A2 = pseudo return address (for emulation core, to emulate prefix -;;; instructions properly) -;;; A1 = scratch -;;; A0 = scratch +;;; A6 = +;;; A5 = instruction table base pointer +;;; A4 = bank 3 base +;;; A3 = bank 2 base +;;; A2 = bank 1 base +;;; A1 = bank 0 base +;;; A0 = ;;; -;;; D0 = current instruction -;;; D1 = scratch +;;; D0 = current instruction, scratch for macros +;;; D1 = scratch for instructions ;;; ;;; D2 = emulated SP, PC SP high, PC low - both virtual addresses ;;; @@ -48,38 +47,78 @@ ;; Macro to read a byte from main memory at register \1. Puts ;; the byte read in \2. FETCHB MACRO ; 14 cycles, 4 bytes + ;; XXX deref move.b 0(a6,\1.w),\2 ENDM ;; Macro to write a byte in \1 to main memory at \2 (regs only) PUTB MACRO ; 14 cycles, 4 bytes + ;; XXX deref move.b \1,0(a6,\2) ENDM ;; Macro to read a word from main memory at register \1 ;; (unaligned). Puts the word read in \2. -FETCHW MACRO ; 32 cycles, 10 bytes +FETCHW MACRO + ;; XXX call deref + move.b 1(a6,\1.w),\2 ; 14/4 ror.w #8,\2 ; 4/2 move.b 0(a6,\1.w),\2 ; 14/4 ENDM ;; Macro to write a word in \1 to main memory at \2 (regs only) - ;; XXX ALIGNMENT PUTW MACRO ; 14 cycles, 4 bytes + ;; XXX ALIGNMENT move.b \1,0(a6,\2) ENDM + ;; Push the word in \1 (register) using stack word register d2 + ;; (must be pre-swapped). + ;; Destroys d0, d1, a0. + + ;; (SP-2) <- \1_l + ;; (SP-1) <- \1_h + ;; SP <- SP - 2 +PUSHW MACRO + subq.w #1,d1 + move.w d2,d1 + bsr deref + move.b \1,(a0) ; \1_l + subq.w #1,d1 + bsr deref + move.b \1,(a0) ; \1_h + subq.w #2,d2 + ENDM + + ;; Pop the word at the top of stack d2 (pre-swapped) into \1. + ;; Destroys d0, a0. +POPW MACRO + move.b d2,d1 + bsr deref ; low byte + move.b (a0),\1 + + LOHI \1 + addq.w #1,d1 + bsr deref ; high byte + move.b (a0),\1 + HILO \1 + addq.w #2,d2 + ENDM + ;; == Immediate Memory Macros == ;; Macro to read an immediate byte into \1. -FETCHBI MACRO ; 18 cycles, 6 bytes +FETCHBI MACRO ; 40 cycles, 14 bytes addq.w #1,d2 ; 4/2 - move.b -1(a6,d2.w),\1 ; 14/4 + move.w d2,d1 ; 4/2 + bsr deref ; 18/6 + move.b (a0),\1 ; 14/4 ENDM ;; Macro to read an immediate word (unaligned) into \1. FETCHWI MACRO ; 36 cycles, 12 bytes + ;; XXX use deref addq.w #2,d2 ; 4/2 move.b -1(a6,d2.w),\1 ; 14/4 rol.w #8,d2 ; 4/2 @@ -167,12 +206,33 @@ _main: include "flags.asm" emu_setup: - movea emu_plain_op,a3 + movea emu_plain_op,a5 movea emu_fetch(pc),a2 ;; XXX finish + rts -refresh: ; screen refresh routine - ;; XXX Do this + + + ;; 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 #$C000,d0 + rol.w #5,d0 + jmp 0(pc,d0) + ;; 00 + movea a1,a0 + bra deref_go + ;; 01 + movea a2,a0 + bra deref_go + ;; 02 + movea a3,a0 + bra deref_go + ;; 03 + movea a4,a0 +deref_go: + adda d1,a0 rts ;; ========================================================================= @@ -194,7 +254,7 @@ emu_fetch: eor.w d0,d0 ; 4 cycles move.b (a4)+,d0 ; 8 cycles rol.w #5,d0 ; 4 cycles adjust to actual alignment - jmp 0(a3,d0) ;14 cycles + jmp 0(a5,d0) ;14 cycles ;; overhead: 30 cycles ;;; ======================================================================== @@ -370,7 +430,7 @@ emu_op_11: ; S emu_op_12: ;; LD (DE),A ;; No flags - move.b 0(a0,d5.w),d3 + FETCHB d5,d3 DONE START @@ -1618,6 +1678,7 @@ emu_op_ae: emu_op_af: ;; XOR A F_XOR_B d3,d3 + ;; XXX DONE @@ -1690,6 +1751,7 @@ emu_op_b7: ;; COMPARE instruction F_CP_B MACRO + ;; XXX ENDM START @@ -1761,19 +1823,28 @@ emu_op_c0: DONE START -emu_op_c1: +emu_op_c1: ; S16 T44 ;; POP BC + swap d2 + FETCHWI d4 + swap d2 + DONE START emu_op_c2: ;; JP NZ,immed.w ;; if ~Z ;; PC <- immed.w + bsr f_norm_z + bne emu_op_c3 + DONE START -emu_op_c3: +emu_op_c3: ; S12 T36 ;; JP immed.w ;; PC <- immed.w + FETCHWI d2 + DONE START emu_op_c4: @@ -1783,37 +1854,53 @@ emu_op_c4: START emu_op_c5: ;; PUSH BC + swap d2 + PUSHW d4,d2 + swap d2 + DONE START emu_op_c6: ;; ADD A,immed.b + FETCHBI d1 + F_ADD_B d1,d3 + DONE START emu_op_c7: ;; RST immed.b ;; CALL 0 + ;; XXX check + move.l d2,d1 + swap d1 ; d1 has SP + PUSHW d2 ; d1=SP implicit + clr.w d1 + FETCHW d1,d2 ; ($0000) + DONE START emu_op_c8: ;; CALL immed.w + ;; (Like JSR on 68k) ;; (SP-1) <- PCh ;; (SP-2) <- PCl ;; SP <- SP - 2 ;; PC <- address + move.l d2,d1 ; d1 has PC + swap d2 ; d2 has SP + PUSHW d1 ; slow ... but CALL is slow. + swap d2 + FETCHWI d2 + DONE START emu_op_c9: ;; RET ;; PCl <- (SP) - ;; PCh <- (SP+1) + ;; PCh <- (SP+1) POPW ;; SP <- (SP+2) swap d2 - FETCHB d2,d1 - addq.b #1,d2 - LOHI d1 - FETCHB d2,d1 - HILO d1 - addq.b #1,d2 + POPW d1 swap d2 move.w d1,d2 DONE |