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Forums > C64 Coding > drivecoding
2004-03-11 15:01
Oswald

Registered: Apr 2002
Posts: 5094
drivecoding

Hi people!

I have looked for info on the topic with google, but I think there is very little info on this out there. Anyone can post some useful links?

other questions:

- anyone can give me a sourcecode which would upload any kind of prg to the drive, and execute it ?
- why atn cant be used to send bits ?
- where is the entry point in the drive rom of the soft reset routine?
2004-03-11 15:24
cadaver

Registered: Feb 2002
Posts: 1160
Once in my life I was in similar position, therefore I wrote the fastloader rants at covertbitops :)

I recommend:

Marko Mäkelä's adaptation/rework of GI JOE loader, can be tricky with all conditional defines for C64/VIC20 etc.

http://www.ffd2.com/fridge/io/irqloader.s

My fastloader rants + the loadersystem

http://www.student.oulu.fi/~loorni/covert/rants/irqload.htm
http://www.student.oulu.fi/~loorni/covert/rants/2bitload.htm
http://www.student.oulu.fi/~loorni/covert/tools/loader.zip

Cybernator's loader (does everything hard way, no drive-rom routine support used)

http://www.geocities.com/lazeristoski/ctsload.zip

ATN can be used by the computer as a timing signal, but the drive must anticipate each ATN bit value and set another bit in its serial bus register ($1800), otherwise it pulls DATA low automatically because of a circuit designed to respond to the ATN. Because of DATA pulled low by all other drives on the bus, it will work with only one drive.

The reset vector can be reached by doing jmp ($fffa). But I've found it nicest to exit by jumping to the Initialize routine $d005, so that one can safely mess with all the drive-ram buffers one wants, including the BAM..
2004-03-11 15:26
Radar
Account closed

Registered: Jul 2003
Posts: 259
Quote: Hi people!

I have looked for info on the topic with google, but I think there is very little info on this out there. Anyone can post some useful links?

other questions:

- anyone can give me a sourcecode which would upload any kind of prg to the drive, and execute it ?
- why atn cant be used to send bits ?
- where is the entry point in the drive rom of the soft reset routine?


Look at all IFFL-routines back from 90-92. The scanner-code has been sent into the 1541-memory and got executed. That's the way we liked it ;-) Afterwards you can read bits/bytes out of the routine. Why not reading the 'Big 1541 Book' from Data Becker from 1988? There you will find all solutions to all your questions...
2004-03-11 15:28
cadaver

Registered: Feb 2002
Posts: 1160
Ah, a mistake, reset vector is of course at $fffc. Btw I would be interested in sourcecode of IFFL routines too but all readily available sources, according to my searches, seem to be lame (ie. not real scanning IFFL, but instead read bytes off the file until correct position reached)
2004-03-11 16:01
Radar
Account closed

Registered: Jul 2003
Posts: 259
Quote: Ah, a mistake, reset vector is of course at $fffc. Btw I would be interested in sourcecode of IFFL routines too but all readily available sources, according to my searches, seem to be lame (ie. not real scanning IFFL, but instead read bytes off the file until correct position reached)

Nah, that's just a trick just like reading seq-files and then calculating t/s/b. Look at the public ftp's and you'll find something neat then, eg. arnold-ftp

And btw, why did you start 3 threads with the same question?
2004-03-12 08:26
Graham
Account closed

Registered: Dec 2002
Posts: 990
@oswald:

sending stuff to drive is fairly easy:

; send LISTEN to drive:
LDA $BA ; device number (usually 8)
JSR $FFB1 ; LISTEN
LDA #$6F ; secondary adress (15)
JSR $FF93 ; SECLSN

; send M-W command to drive:
LDA #"M"
JSR $FFA8 ; IECOUT
LDA #"-"
JSR $FFA8
LDA #"W"
JSR $FFA8

; send adress and size to drive:
LDA #$00 ; adress in drive (low byte)
JSR $FFA8
LDA #$04 ; adress in drive (high byte)
JSR $FFA8
LDA #$20 ; 32 bytes
JSR $FFA8

; transfer stuff:
LDY #$00
.bla
LDA drivestuff,Y
JSR $FFA8
INY
CPY #$20
BNE .bla

; send UNLISTEN to drive:
JSR $FFAE ; UNLSN

that's it. the maximum transfer size in one go is 36 bytes, so typically people will use the M-W command in 32 bytes chunks.
2004-03-12 09:09
Oswald

Registered: Apr 2002
Posts: 5094
thanks for all the help so far!

atn seems to be quite tricky.

$1800:

Bit #4: ATNA OUT; 1 = Enable device presence detection by acknowledging ATN IN signals on DATA OUT
Bit #7: ATN IN; 0 = Low; 1 = High.


so this means, that bit 4 must be set high, to be able to read a high ATN signal on bit 7 ? but when c64 sets atn high this will also pull DATA to 0 ?

it looks that atn then can set to low by the c64 without bit 4 in 1800 being high, this is what I saw in krill's sources.

can anyone verify that this works the way I wrote?:)
2004-03-12 09:17
Graham
Account closed

Registered: Dec 2002
Posts: 990
if you want to read ATN IN you must set ATN OUT to 0, same with DATA and CLK. same with $DD00 in the c64, with the difference that the two IN bits are inverted there.
2004-03-12 10:42
Oswald

Registered: Apr 2002
Posts: 5094
this is how krill did it:
(hope he wont mind, he released the source to public anyway)

LDA #$00
STA $1800 ;ATN 2 LO
BIT $1800
BPL *-3 ;wait 4 ATN LO
DSENDLUP LDX GCRSPLT3+1,Y
LDA NUGCRDEC-$09,X
LDX GCRSPLT2+1,Y
BIT $1800 ;wait 4 ATN HI
BMI *-3
STA $1800 ;send 2 bits
ASL A
ORA #%00010000
BIT $1800 ;wait 4 ATN LO
BPL *-3
STA $1800 ;send 2 bits,ATN to HI
LDA NUGCRDEC-$09,X
BIT $1800 ;wait 4 ATN HI
BMI *-3
STA $1800 ;send 2 bits ATN to LO
ASL A
ORA #%00010000
BIT $1800 ;wait 4 ATN LO
BPL *-3

why does he need to set atn out to high every second time?
maybe atn high can only be read when atn out is also high?
aint it possible to read atn lo/hi state leaving atn out 0 all the time?
2004-03-12 11:01
Hoogo

Registered: Jun 2002
Posts: 105
If I remember it correctly, DATA works fine when ATN OUT of the floppy and of the C64 have the same value. It is part of the serial protocol that all devices on the bus shall pull Data down when ATN is set. In the 1541 that was partly done in hardware and partly in software. But I don't remember the exact meaning.
2004-03-12 14:24
Oswald

Registered: Apr 2002
Posts: 5094
Quote: if you want to read ATN IN you must set ATN OUT to 0, same with DATA and CLK. same with $DD00 in the c64, with the difference that the two IN bits are inverted there.

it doesnt quite looks so in krill's source, he reads ATN IN without taking care of the state of DATA and CLK, but there is this fiddling with ATN OUT, even he cant explain why its there...
 
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