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Peiselulli
Registered: Oct 2006
Posts: 81 |
1541 low level programming problem
Hello,
I have a problem that I don't understand. I tried the
following code for the 1541 :
jsr $F97E ; MOTOR_ON
jsr $fe00 ; SET_READ_MODE
loop
BIT $1C00 ; SYNC signal
BMI loop ; not yet found?
LDA $1C01 ; read byte
lda $1c00
eor #$08
sta $1c00
CLV
-
bvc -
lda $1c01
jmp loop
I expect (if a floppy is inserted) that the LED flickers, but it does not. If I remove the "bvc" command, it works like expected. Has anybody a idea what I have forgotten to initialize ?
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Peiselulli
Registered: Oct 2006
Posts: 81 |
yes, it did.
is there something to initalize that i have forgotten ?
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Krill
Registered: Apr 2002
Posts: 2854 |
Also from my loader:
lda #CB2_OUTPUT_HIGH | CB1_IRQ_ON_NEG_ACTIVE_EDGE | CA2_OUTPUT_HIGH | CA1_IRQ_ON_NEG_ACTIVE_EDGE
sta VIA2_PCR
This is an lda #$ee sta $1c0c, maybe that fixes it? |
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Peiselulli
Registered: Oct 2006
Posts: 81 |
many thanks, that was missing !
now it flickers :->
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Krill
Registered: Apr 2002
Posts: 2854 |
Greatness :) |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
Also, I'd add a wait loop after turning the motor on. It takes some time until it has 100% speed.
Oh and for searching a sync, you can use the routine at $F556. |
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