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xasm/doc/xbootstd.asx

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1999-09-09 23:20:00 +00:00
* Boot executable file loader coded by Fox/Taquart
* Reads file from ATR prepared with X-BOOT.
* Standard loader - ROM and interrupts enabled.
opt h-
org $780
bufr equ $700 128-byte buffer
tp equ $43 Temporary byte
vc equ $44 Start and end vectors (4 bytes)
* Boot code
boot dta b(0,1),a(boot,$e477) Boot header
txtpos equ 215
ldy #txtpos Print text
print mva text-txtpos,y ($58),y+
cpy #txtpos+txtlen
bcc print
mwa #rts $2e0 Set default run vector
mva >bufr $305 Set buffer address
mva #$ff ^31 Turn BASIC off
dta b({lda a:0}) Skip two bytes
secrts sec Return with error
rts rts
mva:pha >rts $2e3 Set init address...
mva:pha <rts $2e2 ... and put return address on stack
ldx #-5 Load header
hput sta vc+4,x+ Store byte of header
stx tp
next inc bufx Increment buffer index
bpl getx Branch if within buffer
inw $30a Increment sector number
jsr $e453 Read sector
bmi secrts Exit on error
asl bufx Change $80 to $00
getx lda bufr+$7f Get byte from buffer
bufx equ *-2 Buffer index
ldx tp Check if header or block data
bne hput Branch to store header
sta (vc,x) Store block data
inw vc Increment vector
lda vc+2 Check if end of block reached
cmp vc
lda vc+3
sbc vc+1
bcs next No: read next byte
mva #3 ^2f Yes: Reset POKEY...
init jmp ($2e2) ... and call init routine
text dta d'Loading... '
txtlen equ *-text
dta c'5.0' Unused boot sector space
1999-09-09 23:20:00 +00:00
ert *<>boot+$80 Exactly 128 bytes should be used
* X-BOOT adds this block at the end of loaded file
* It changes jmp ($2e2) to jmp ($2e0)
opt h+
org init+1
dta l($2e0)
end