mirror of https://github.com/LemonBoy/grape.git
256 lines
4.7 KiB
ArmAsm
256 lines
4.7 KiB
ArmAsm
.arm
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.section .itcm,"ax",%progbits
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.global readb
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.global writeb
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.global mem_reset
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.global mainram
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.global lcram
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.global jstk_btn
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.global jstk_axis
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.global memmap_w
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.global memmap_r
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.global keybd_latch
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.global jstk_rst_cycle
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.global page_dirty
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// uint8_t readb (uint16_t addr)
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readb:
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mov r1, r0, lsr #8
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cmp r1, #0xc0
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beq 1f
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mov r1, r1, lsr #4
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ldr r2, =memmap_r
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ldr r3, [r2, r1, lsl #2]
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ldrb r0, [r3, r0]
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bx lr
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// IO Read @ 0xc000
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1: and r1, r0, #0xf0
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ldr pc, [pc, r1, lsr #2]
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nop
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io_read_tbl:
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.word io_keybd
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.word io_keybdl
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.word io_null
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.word io_spkr
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.word io_null
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.word video_io_read
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.word io_jstk
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.word io_jstk_rst
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.word io_lc
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.word io_null
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.word io_null
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.word io_null
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.word io_null
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.word io_null
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.word disk_io_read
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.word io_null
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.ltorg
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// void writeb (uint16_t addr, uint8_t val)
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writeb:
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mov r2, r0, lsr #8
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cmp r2, #0xc0
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// IO Read
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beq 1f
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mov r2, r2, lsr #2
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// Mark the page as dirty
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mov r3, #1
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ldr r12, =page_dirty
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strb r3, [r12, r2]
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mov r2, r2, lsr #2
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ldr r12, =memmap_w
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ldr r3, [r12, r2, lsl #2]
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strb r1, [r3, r0]
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bx lr
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1: and r1, r0, #0xf0
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ldr pc, [pc, r1, lsr #2]
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nop
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io_write_tbl:
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.word io_null
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.word io_keybdl
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.word io_null
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.word io_null
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.word io_null
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.word video_io_read
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.word io_jstk_rst
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.word io_null
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.word io_lc
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.word io_null
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.word io_null
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.word io_null
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.word io_null
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.word io_null
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.word disk_io_read
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.word io_null
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.ltorg
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// IO handlers
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io_keybd:
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ldr r2, =keybd_latch
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ldr r0, [r2]
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bx lr
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io_keybdl:
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ldr r2, =keybd_latch
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ldr r0, [r2]
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// Clear the latch
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and r0, #0x7f
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str r0, [r2]
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bx lr
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io_jstk:
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and r0, #0xf
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ldr r1, =(jstk_btn-4)
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cmp r0, #0x4
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ldr r0, [r1, r0, lsl #2]
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// Handle the pushbutton status
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bxlo lr
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ldr r1, [r1, #32] // jstk_rst_cycle
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// Check how many cycles have passed
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subs r2, r1, r5
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ldrmi r3, =17030
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addmi r2, r3
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// Should the paddle be sent low ?
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cmp r2, r0
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movls r0, #0x80
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movhi r0, #0x00
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bx lr
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io_jstk_rst:
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ldr r0, =jstk_rst_cycle
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str r5, [r0]
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// Read KEYINPUT
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ldr r3, =0x4000130
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ldrh r3, [r3]
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// Find how many cycles the joystick counter takes to return to 0
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mvn r3, r3, lsr #4
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adr r2, axis_to_cycles
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and r3, #0xf
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add r2, r3, lsl #2
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ldrh r1, [r2, #0]
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str r1, [r0, #-16]
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ldrh r1, [r2, #2]
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str r1, [r0, #-12]
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bx lr
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// The pdlread routine takes 11 cycles
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axis_to_cycles:
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.short 0x7f*11,0x7f*11 //
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.short 0xff*11,0x7f*11 // R
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.short 0x00*11,0x7f*11 // L
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.short 0x00*11,0x7f*11 // R+L
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.short 0x7f*11,0x00*11 // U
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.short 0xff*11,0x00*11 // R+U
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.short 0x00*11,0x00*11 // L+U
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.short 0x00*11,0x00*11 // R+L+U
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.short 0x7f*11,0xff*11 // D
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.short 0xff*11,0xff*11 // R+D
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.short 0x00*11,0xff*11 // L+D
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.short 0x00*11,0xff*11 // R+L+D
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.short 0x7f*11,0xff*11 // U+D
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.short 0xff*11,0xff*11 // R+U+D
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.short 0x00*11,0xff*11 // L+U+D
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.short 0x00*11,0xff*11 // R+L+U+D
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io_lc:
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ldr r12, =memmap_w
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ldr r3, =(mainram+0x4000)
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// Do it backwards so we can reuse r3
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str r3, [r12, #0xf<<2]
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str r3, [r12, #0xe<<2]
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// Select between bank 1/2
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tst r0, #8
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mov r2, r3
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subne r2, #0x1000
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str r2, [r12, #0xd<<2]
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// Check if rom is mapped on read
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ldr r1, =map_rom_tbl
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and r0, #3
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ldr r0, [r1, r0, lsl #2]
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ldr r12, =memmap_r
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tst r0, #1 // this is lame
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bne 1f // map the rom
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str r2, [r12, #0xd<<2]
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str r3, [r12, #0xe<<2]
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str r3, [r12, #0xf<<2]
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bx lr
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1: sub r3, #0x4000
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str r3, [r12, #0xd<<2]
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str r3, [r12, #0xe<<2]
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str r3, [r12, #0xf<<2]
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bx lr
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io_spkr:
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mov r0, r5
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ldr r1, =sound_spkr_flip
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bx r1
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io_null:
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mov r0, #0
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bx lr
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mem_reset:
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ldr r0, =memmap_r
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ldr r1, =memmap_w
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ldr r2, =mainram
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mov r3, #0x10
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1: str r2, [r0], #4
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str r2, [r1], #4
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subs r3, #1
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bne 1b
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bx lr
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.ltorg
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.bss
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.align 4
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mainram:
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.space 0x10000
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lcram:
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.space 0x1000*4
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.section .dtcm
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.align 4
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memmap_r:
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.rept 16
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.word mainram
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.endr
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memmap_w:
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.rept 16
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.word mainram
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.endr
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page_dirty:
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.rept 64
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.byte 0
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.endr
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// A button is active when the 7th bit is set
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jstk_btn:
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.word 0 // PB1
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.word 0 // PB2
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.word 0 // PB3 (shift)
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// Axis are 0 <= x <= 255, where 0x80 is center
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jstk_axis:
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.word 0 // P1 X
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.word 0 // P1 Y
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.word 0 // P2 X
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.word 0 // P2 Y
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// io_jstk_rst relies on this to be after the joystick
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// data for correct indexing. Don't move.
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jstk_rst_cycle:
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.word 0
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keybd_latch:
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.word 0
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.section .rodata
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map_rom_tbl:
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.word 0,1,1,0
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