c2t/asm/diskload9600.s
2014-11-23 17:26:22 -07:00

175 lines
3.7 KiB
ArmAsm

;diskload9600.s
org = $9000 ; should be $9000
cout = $FDED ; character out sub
crout = $FD8E ; CR out sub
prbyte = $FDDA ; print byte in hex
tapein = $C060 ; read tape interface
warm = $FF69 ; back to monitor
clear = $FC58 ; clear screen
endbas = $80C
target = $1000
; zero page parameters
begload = $00 ; begin load location LSB/MSB
endload = $02 ; end load location LSB/MSB
chksum = $04 ; checksum location
pointer = $0C ; LSB/MSB pointer
start:
.org endbas
move: ; end of BASIC, move code to readtape addr
ldx #0
move1:
lda moved,x
sta readtape,x
; lda moved+256,x
; sta readtape+256,x
inx
bne move1
phase1:
jsr crout ; print LOADING...
lda #<loadm
ldy #>loadm
jsr print
; diskload2 ORG
lda #$D0 ; store begin location LSB
sta begload
lda #$96 ; store begin location MSB
sta begload+1
; end of DOS + 1 for comparison
lda #$00 ; store end location LSB
sta endload
lda #$C0 ; store end location MSB
sta endload+1
jsr readtape ; get the code
jmp $9700 ; run it
loadm:
.byte "LOADING INSTA-DISK, ETA "
loadsec: ; 10 bytes for "XX SEC. ",$00
.byte 0,0,0,0,0,0,0,0,0,0
moved:
.org org ; $9000
readtape:
lda begload ; load begin LSB location
sta store+1 ; store it
lda begload+1 ; load begin MSB location
sta store+2 ; store it
lda #$ff ; init checksum
sta chksum
wait: bit tapein
bpl wait
waithi: bit tapein ; Wait for input to go high.
bmi waithi
pre: lda #1 ; Load sentinel bit
ldx #0 ; Clear data index
clc ; Clear carry (byte complete flag)
data: bcc waitlo ; Skip if byte not complete
store: sta target,x ; Store data byte
eor chksum ; compute checksum
sta chksum ; store checksum
lda #1 ; Re-load sentinel bit
waitlo: bit tapein ; Wait for input to go low
bpl waitlo
bcc poll9 ; Poll at +9 cycles if no store
inx ; Stored, so increment data index
bne poll13 ; Poll at +13 cycles if no carry
inc store+2 ; Increment data page
bne poll21 ; (always) poll at +21 cycles
one: sec ; one bit detected
rol ; shift it into A
jmp data ; and go handle data (C = sentinel)
zero: clc ; zero bit detected
rol ; shift it into A
jmp data ; and go handle data (C = sentinel)
poll9: bit tapein
bpl zero ; zero bit (short)(9-15 cycles)
poll13: bit tapein ; (2 cycles early if branched here)
bpl zero ; zero bit (15-21 cycles)
poll21: bit tapein
bpl zero ; zero bit (21-27 cycles)
bit tapein
bpl zero ; zero bit (27-33 cycles)
bit tapein
bpl zero ; zero bit (33-39 cycles)
bit tapein
bpl zero ; zero bit (39-45 cycles)
bit tapein
bpl zero ; zero bit (45-51 cycles)
bit tapein
bpl zero ; zero bit (51-57 cycles)
bit tapein
bpl zero ; one bit (57-63 cycles)
bit tapein
bpl one ; one bit (63-69 cycles)
bit tapein
bpl one ; one bit (69-75 cycles)
bit tapein
bpl one ; one bit (75-81 cycles)
bit tapein
bpl one ; one pulse (81-87 cycles)
bit tapein
bpl pre ; pre pulse (87-93 cycles)
bit tapein
bpl pre ; pre pulse (93-99 cycles)
bit tapein
bpl pre ; pre pulse (99-105 cycles)
; low freq signals end of data
endcode:
txa ; write end of file location + 1
clc
adc store+1
sta store+1
bcc endcheck ; LSB didn't roll over to zero
inc store+2 ; did roll over to zero, inc MSB
endcheck: ; check for match of expected length
lda endload
cmp store+1
bne error
lda endload+1
cmp store+2
bne error
jsr ok
sumcheck:
jsr crout
lda #<chkm
ldy #>chkm
jsr print
lda chksum
bne error
jmp ok ; return to caller
error:
lda #<errm
ldy #>errm
jsr print
jmp warm
ok:
lda #<okm
ldy #>okm
print:
sta pointer
sty pointer+1
ldy #0
lda (pointer),y ; load initial char
print1: ora #$80
jsr cout
iny
lda (pointer),y
bne print1
rts
chkm: .asciiz "CHKSUM "
okm: .asciiz "OK"
errm: .asciiz "ERROR"
end: