- Changed to use $c000-dfff instead of $a000-bfff, saving 4K by overlapping I/O area. Decode table can be moved to a different 4K block if needed.
- Fixed Esc broken in 1.1 due to copy and paste bug - Removed unnecessary display paging
This commit is contained in:
Simon Owen
parent
6d9b0f4f0d
commit
e712035197
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@ -4,7 +4,7 @@
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;
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; WWW: http://simonowen.com/sam/apple1emu/
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base: equ &a000 ; Spare-ish Apple 1 space
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base: equ &d000 ; Emulator code shares Apple 1 I/O area
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status: equ &f9 ; Status and extended keyboard port
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lmpr: equ &fa ; Low Memory Page Register
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@ -25,10 +25,11 @@ m6502_nmi: equ &fffa ; nmi vector address
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m6502_reset: equ &fffc ; reset vector address
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m6502_int: equ &fffe ; int vector address (also for BRK)
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r1onclbc: equ &01ea ; ROM 1 on, call BC
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getkey: equ &1cab ; SAM ROM key reading (NZ=got key in A, A=0 for no key)
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; Apple 1 keyboard and display I/O locations
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; PIA registers for keyboard and display I/O
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kbd_data: equ &d010 ; keyboard data
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kbd_ctrl: equ &d011 ; keyboard control
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@ -41,17 +42,26 @@ dsp_ctrl: equ &d013 ; display control
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dump $
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autoexec
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start: di
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di
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jr start
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ld a,low_page+rom0_off
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defs kbd_data-$
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; This gap contains the PIA locations from above
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defs dsp_ctrl-kbd_data+1
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start: ld a,low_page+rom0_off
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out (lmpr),a
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ld a,vmpr_mode2+screen_page
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out (vmpr),a
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ld (basic_stack),sp
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ld sp,stack_top
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call set_sam_attrs ; set the mode 2 attrs so the screen is visible
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call setup_im2 ; enable IM 2
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ld a,(op_00) ; lowest address used by emulator
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ld (rom_write+1),a ; save byte to restore to simulate ROM
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reset_loop: ld hl,0
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ld (dsp_data),hl ; display ready
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ld (kbd_data),hl ; no key available
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@ -243,10 +253,6 @@ file_skip: ld a,(hl) ; fetch next file character
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jr nz,file_done
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ld a,&0d ; convert LF to CR
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file_done: ld (filepos),hl
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ex af,af'
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ld a,screen_page+rom0_off
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out (lmpr),a
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ex af,af'
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and a
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ret
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filepos: defw 0
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@ -282,7 +288,6 @@ update_io:
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ld a,&c9 ; RET opcode
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ld (main_loop),a ; return to reset on next instruction
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not_reset:
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jr c,got_key ; unshifted gives chr
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still_esc: ld a,&f7
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in a,(status)
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@ -315,13 +320,13 @@ not_sym:
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call get_filekey ; got a type-in key from file?
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jr nz,got_key ; jump if we have
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skip_key: ld a,&1f+rom1_on
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skip_key: ld a,&1f ; LMPR page for BASIC, with ROM 0 enabled
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out (lmpr),a
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call getkey
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ex af,af'
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ld a,screen_page+rom0_off
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out (lmpr),a
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ex af,af'
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ld (save_stack),sp
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ld sp,(basic_stack)
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ld bc,getkey ; return key code in A, zero for none
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call r1onclbc
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ld sp,(save_stack)
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jr z,no_key
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call map_key
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and a
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@ -343,6 +348,8 @@ no_key:
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cp &7f
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jr z,done_draw
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push af
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ld a,screen_page+rom0_off
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out (lmpr),a ; page in screen
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ld a,&00 ; space
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call display_chr ; erase cursor
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pop af
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@ -392,11 +399,7 @@ im2_handler: push af
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in a,(lmpr)
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push af
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ld a,screen_page+rom0_off
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out (lmpr),a
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call update_io
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pop af
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out (lmpr),a
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@ -425,6 +428,9 @@ im2_table: defs 257
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stack_top: ; stack fits nicely in the slack space
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im2_jp: jp im2_handler
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basic_stack: defw 0
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save_stack: defw 0
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@ -442,7 +448,7 @@ i_undoc_1: jp (ix) ; NOP
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read_write_loop:
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write_loop: ld a,h
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cp base/256 ; emulator or ROMs above?
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cp op_00/256 ; MSB of lowest emulator byte
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jr nc,write_trap
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zwrite_loop:
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@ -454,8 +460,8 @@ main_loop: ld a,(de) ; 7/7/15 - fetch opcode
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jp (hl) ; 4/5/9 - execute!
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; = 35T (official) / 40T (off-screen) / 72T (on-screen)
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write_trap: cp &d0
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jr nz,write_rom
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write_trap: cp &d0 ; I/O page?
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jr nz,rom_write
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ld a,l
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cp &12 ; display char?
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jr z,chr_write
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@ -463,8 +469,8 @@ write_trap: cp &d0
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chr_write: set 7,(hl) ; display busy
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jp (ix)
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write_rom: ld a,&f3 ; Z80 DI opcode
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ld (base),a ; emulator appears to be in ROM for RAM tests
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rom_write: ld a,&00 ; patched by starting code
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ld (op_00),a ; emulator appears read-only to be ROM for RAM tests
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jp (ix)
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read_loop: ld a,h
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