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Switch to use DMA and clean up boot code

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pjht 2022-11-21 10:39:29 -06:00
parent 52d5e67f44
commit cbcb7010c6
2 changed files with 10 additions and 22 deletions
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boot/boot.68k
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@ -22,21 +22,20 @@ phead_loop:
move.l (a0), d1 | If the type of the program header isn't 1 (LOAD), skip the header move.l (a0), d1 | If the type of the program header isn't 1 (LOAD), skip the header
cmpi.l #0x1, d1 cmpi.l #0x1, d1
bne.b next_seg bne.b next_seg
| Zero the destination memory of the program header | Zero the destination memory
move.l (20, a0), d1 | Put the memory size of the program header - 1 in d1 move.l (20, a0), d1 | Put the memory size - 1 in d1
subq.l #0x1, d1 subq.l #0x1, d1
move.l (8, a0), a1 | Put the starting memory address of the program header in a1 move.l (8, a0), a1 | Put the starting memory address in a1
zero_loop: zero_loop:
move.b #0, (a1)+ | Zero a byte of the destination memory move.b #0, (a1)+ | Zero a byte of the destination memory
dbra d1, zero_loop | Loop back if there is more to zero dbra d1, zero_loop | Loop back if there is more to zero
| Copy the data of the program header from the loaded file into position | Copy the data from the loaded file into position
move.l (16, a0), d1 | Put the file size of the program header - 1 in d1 move.l (16, a0), d1 | Put the file size - 1 in d1
beq.b next_seg | If the file size is 0, skip the copy (ex, .bss section)
subq.l #0x1, d1 subq.l #0x1, d1
cmpi.l #0xFFFFFFFF, d1 | If the file size is 0, skip the copy (ex, .bss section) move.l (4, a0), a1 | Put the address of the loaded data in a1
beq.b next_seg
move.l (4, a0), a1 | Put the address of the start of the loaded program header's data in a1
adda.l #0xA000, a1 adda.l #0xA000, a1
move.l (8, a0), a2 | Put the starting memory address of the program header in a2 move.l (8, a0), a2 | Put the starting memory address in a2
load_loop: load_loop:
move.b (a1)+, (a2)+ | Copy a byte of data into position move.b (a1)+, (a2)+ | Copy a byte of data into position
dbra d1, load_loop | Loop back if there is more to copy dbra d1, load_loop | Loop back if there is more to copy
@ -68,22 +67,11 @@ ffc_done:
| Destination in a1 | Destination in a1
| Start sector in d0.l | Start sector in d0.l
| Sector count in d1.l | Sector count in d1.l
| Clobbers a1, d1
read_sectors: read_sectors:
move.l d0, (a0) | Set the sector number move.l d0, (a0) | Set the sector number
move.l d1, (4, a0) | Set the sector count move.l d1, (4, a0) | Set the sector count
move.w #0x0, (8, a0) | Issue a read command move.l a1, (0xC, a0) | Set the destination address
| Transfer 0x200 (512) * sector_count bytes from the storage card's data register to (a1) move.w #0x1, (8, a0) | Issue a DMA read command
lsl.l #8, d1 | d0 = d0 * 256 to compute the number of words to transfer
subq.l #0x1, d1 | Subtract 1 from the word count to account for the extra loop done by dbra
bra.b rs_loop
rs_loop_swap:
swap.w d1
rs_loop:
move.w (0xA, a0), (a1)+ | Transfer a word of sector data to the destination
dbra.w d1, rs_loop
swap.w d1
dbra.w d1, rs_loop_swap
rts rts
.if . != 512 .if . != 512

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rom.bin
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