grape/source/mem.s
2013-10-13 18:31:57 +00:00

256 lines
4.7 KiB
ArmAsm

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