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Read size of file in sectors

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Byron Lathi
2023-08-23 20:45:09 -07:00
parent 9b1576774b
commit 8273e01ad8
1 changed files with 46 additions and 10 deletions
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56
sw/bios/boot2.s
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@@ -9,6 +9,7 @@
.MACPACK generic
fatbuf = $A000
filebuf = $B000
.segment "BOOTLOADER"
@@ -96,22 +97,57 @@ _start:
ldx #>_good
jsr _cputs ; otherwise continue on
; Now we need to load it into memory. It cannot be just loaded into memory,
; I think if we have startup be first in the linker script it will always be
; at the beginning? then we can just copy the text/data segments as is...
lda #<word_str
ldx #>word_str
jsr pushax
; parse root directory for kernel.o65
; load first data cluster (we know this is root.)
; If kernel is not in this then we can go read the FAT
; later. Saves time if kernel is near beginning
ldy #$1d ; load file size (256)
lda (ptr3),y
lsr ; divide by 2 to get file size (512)
jsr pusha0
ldy #$4
jsr _cprintf
; bootsector should still be loaded at $8000
; data start should still be valid
ldy #$1b ; load high byte of low first cluster
lda (ptr3),y
tax
dey
lda (ptr3),y ; load low byte of low first cluster
ldx data_start + 1
sec
sbc #$02
bcs @3
dex
@3: asl
asl
asl
clc
adc data_start
bcc @5
inx
@5: stz sreg ; data start is not going to be > 2^16
stz sreg + 1 ; (I hope)
phx
pha
jsr pusheax
lda #<filebuf
ldx #>filebuf
jsr pushax
lda #<ptr1
ldx #>ptr1
jsr _SD_readSingleBlock
lda #<filebuf
ldx #>filebuf
jsr _SD_printBuf
@end: bra @end
str: .asciiz "boot2\r\n"
kernel_str: .asciiz "KERNEL O65"
_good: .asciiz "Found KERNEL"
_good: .asciiz "Found KERNEL\r\n"
word_str: .asciiz "Word Value: %x\r\n"