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prodos-drivers
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No Slot Clock: Shave bytes and better comments 

* Replace BCD->Binary with smaller routine
* Replace most absolute use of $200-7 with stack
* Remove unneeded sentinel byte at end of unlock sequence

Leaves 9 bytes free in driver.
This commit is contained in:
Joshua Bell 2023-01-27 18:29:09 -08:00
parent d9e72d3c1e
commit 1ddae4fab7
1 changed files with 56 additions and 46 deletions
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102
clocks/ns.clock/ns.clock.system.s
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@ -116,14 +116,14 @@ next: inc slot
bne not_found
;; Not found in slot ROM, try main ROMs ???
lda #>$C015
lda #>$C015 ; $C015 = RDCXROM (internal or slot ROM?)
ldy #<$C015
sta ld4+2
sty ld4+1
ldy #$07
ldy #$07 ; $C007 = INTCXROM (read internal ROM)
sta st1+2
sty st1+1
dey
dey ; $C006 = SLOTCXROM (read slot ROM)
sta st4+2
sty st4+1
lda #>$C800
@ -277,83 +277,95 @@ loop: lda driver,y
driver:
php
sei
ld4: lda $CFFF ; self-modified
ld4: lda $CFFF ; self-modified ($CFFF or RDCXROM)
pha
st1: sta $C300 ; self-modified
ld1: lda $C304 ; self-modified
st1: sta $C300 ; self-modified ($Cn00 or INTCXROM)
ld1: lda $C304 ; self-modified ($Cn04)
ldx #8
;; --------------------------------------------------
;; Unlock the NSC by bit-banging.
uloop:
unlock_addr := *+1
lda unlock-1,x ; self-modified
lda unlock-1,x ; self-modified (during relocation)
sec
ror a ; a bit at a time
: pha
lda #0
rol a
tay
ld2: lda $C300,y ; self-modified
ld2: lda $C300,y ; self-modified ($Cn00)
pla
lsr a
bne :-
dex
bne uloop
;; Read 8 bytes * 8 bits of clock data into $200...$207
;; --------------------------------------------------
;; Read 8 bytes * 8 bits of clock data, push onto stack
tmp := $200
ldx #8
bloop: ldy #8
st2:
: lda $C304 ; self-modified
: lda $C304 ; self-modified ($Cn04)
ror a
ror $01FF,x
ror tmp
dey
bne :-
lda $01FF,x ; got 8 bits
lsr a ; BCD to binary
lsr a ; shift out tens
lsr a
lsr a
tay
beq donebcd
lda $01FF,x
and #$0F ; mask out units
clc
: adc #10 ; and add tens as needed
dey
bne :-
sta $01FF,x
donebcd:
;; BCD to Binary - slow but tiny
lda tmp ; A = value
ldy #$FF ; result = -1
sec
sed
: iny ; result += 1
sbc #1 ; value -= 1
bcs :-
cld
tya ; A = result
;; Push to stack
pha
dex
bne bloop
;; Now $200...$207 is y/m/d/w/H/M/S/f
;; --------------------------------------------------
;; Now stack has y/m/d/w/H/M/S/F
;; Update ProDOS date/time.
lda $0204 ; hour
sta TIMELO+1
pla ; year
sta DATELO+1
lda $0205 ; minute
sta TIMELO
pla ; month
asl
asl
asl
asl
asl
sta DATELO
rol DATELO+1
lda $0201 ; month
asl a
asl a
asl a
asl a
asl a
ora $0202 ; day
pla ; day
ora DATELO
sta DATELO
lda $0200 ; year
rol a
sta DATELO+1
pla ; skip week
pla ; hour
sta TIMELO+1
pla ; minute
sta TIMELO
pla ; skip seconds
pla ; skip fraction
;; --------------------------------------------------
;; Finish up
pla
bmi done
st4: sta $CFFF ; self-modified
st4: sta $CFFF ; self-modified ($CFFF or SLOTCXROM)
done: plp
rts
@ -361,12 +373,10 @@ unlock:
;; NSC unlock sequence
.byte $5C, $A3, $3A, $C5
.byte $5C, $A3, $3A, $C5
.byte $00
sizeof_driver := * - driver
.assert sizeof_driver <= 125, error, "Clock code must be <= 125 bytes"
;;; ************************************************************
.ifndef JUMBO_CLOCK_DRIVER
.include "../../inc/driver_postamble.inc"