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2003-03-09 16:06

cadaver

Registered: Feb 2002
Posts: 1153

Opinions on safe minimum $1c07 value?

Any opinions on safe values of $1c07 (disk drive interrupt/head stepper motor frequency on 1541-ish drives)?

I know $3a is the default, and $10 is something one should *never* go below. I quickly checked Remember's recent Gemini Wing release and there $20 was used. So I guess the minimum safe value, considering different disk drive clones etc. would be somewhere between $10-$20?

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2015-05-17 11:20

tlr

Registered: Sep 2003
Posts: 1714

Quote: how about checking if we're on the top/bottom border, and change transfer method for that part ? :) ofcourse sprited would be not allowed in there ;)

That's quite common.

Example (from the Superkit filecopier):

.C:3663  A2 07       LDX #$07
.C:3665  38          SEC
.C:3666  AD 12 D0    LDA $D012
.C:3669  E9 32       SBC #$32
.C:366b  90 04       BCC $3671
.C:366d  29 07       AND #$07
.C:366f  F0 F5       BEQ $3666
.C:3671  8E 00 DD    STX $DD00
.C:3674  48          PHA
.C:3675  68          PLA
.C:3676  24 EA       BIT $EA
.C:3678  AD 00 DD    LDA $DD00
.C:367b  4A          LSR A
.C:367c  4A          LSR A
.C:367d  4D 00 DD    EOR $DD00
.C:3680  4A          LSR A
.C:3681  4A          LSR A
.C:3682  4D 00 DD    EOR $DD00
.C:3685  4A          LSR A
.C:3686  4A          LSR A
.C:3687  A2 27       LDX #$27
.C:3689  4D 00 DD    EOR $DD00
.C:368c  8E 00 DD    STX $DD00

2015-05-17 13:23

DJ Gruby

Registered: Aug 2002
Posts: 29

Krill, you are the God! Thanks so much, now with your change the code seems to work and it doesn't load any garbage anymore, just an original file data:

charin  ldx #$03

charin1 sec
        lda $d012
        sbc #$03
        and #$07
        cmp #$07
        bcs *-9

        lda #$0b
        sta $dd00
        bit $dd00
        bpl charin1

Thanks, you rock!

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