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Forums > CSDb Discussions > Error message: "Found more than one drive on IEC bus" with C128D metal and recent demos
2017-11-08 10:26
Monte Carlos

Registered: Jun 2004
Posts: 258
Error message: "Found more than one drive on IEC bus" with C128D metal and recent demos

Sorry for this lamer question. I use an C128D(metal), currently (although i have used C64 for years until i got room problems with the complete setup).
I have attached a 1541 ultimate and changed the internal 1571 drive to device no 10 by cutting the solder pads. The ultimate has dev no 8. This way i can watch many, mostly old, demos with 1541U. However, the most current demos always complain about more than one drive being enabled. Ok, i thought, plugging off the internal 1571 from the mainbord should fix the problem. I was wrong. The loaders still complain about more than one drive.
Am i wrong with my understanding that plugging off the internal drive also disables the ATN signal?
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2017-11-09 14:22

Registered: Apr 2002
Posts: 952
Looking at the C128DCR (which is the metal C128D) schematics, it very much seems like there is no way of disconnecting the drive electronics from the serial bus, save cutting their traces.

Uploading a small program to the built-in drive that would disable interrupts and set ATNA according to ATN IN in a loop would probably solve your problem, but alas, i have no time right now to hack it up.
2017-11-09 15:24
Monte Carlos

Registered: Jun 2004
Posts: 258
If its not possible to plug of the drive, there should still be the possibility to cut the ATN line and insert a switch instead? After googling i found an howto on herdware, however there is some pic missing.
Somebody knows what they mean with "threethrough-hole solder pads"?
2017-11-09 15:32

Registered: Apr 2002
Posts: 952
Would you really want to cut traces if there's a viable software solution? Poor C128.
2017-11-09 15:34

Registered: Apr 2002
Posts: 952
Also, does the little BASIC line above report a drive on #10, as is expected?
2017-11-09 15:43
Monte Carlos

Registered: Jun 2004
Posts: 258
Can't try it at the moment with my two year boy next to me. Will try in the evening.
2017-11-09 20:45
Monte Carlos

Registered: Jun 2004
Posts: 258
Yes, it shows drive on ID 10.I ridiculously just unplugged the mechanics.btw:hw hack would not be the worst solution for me if it permitted a durable, unproblematic operation of 1541u with my 128dcr.
2017-11-09 20:48

Registered: Apr 2002
Posts: 952
If running a small "shut up everybody who's not #8" program before watching that demo is too much, wellÂ… yeah. :)
2017-11-09 21:11
Monte Carlos

Registered: Jun 2004
Posts: 258
I did already with this

#include <cbm.h>
#include <stdio.h>

char openFile(void){
	char openErr;
	if ( (openErr = cbm_k_open()) ){
		printf("Open failed: Return value = %d\n", openErr);	
	return openErr;

void main(void){
	char drivecmd[] = "u0>\x09";
	char openErr;
	cbm_k_setlfs (15, 8,15);
	cbm_k_setnam (drivecmd);
	if ( !(openErr = openFile()) ){
		printf("Successfully changed device\n");
		printf("Could not change device\n");

and this

OPEN 1,ID,15,"M-W"+CHR$(119)+CHR$(0)+CHR$(2)+CHR$(0)+CHR$(0):CLOSE 1 

My software solution attemps were not of much use up to now.
However, your drive code suggestion is different.
I could place an installation code into the root dir of the 1541U usb stick, so that i could execute it anytime before watching demos.
Didn't know that ATN call and answer chain could be influenced by software.
2017-11-09 21:32

Registered: Apr 2002
Posts: 952
The ATN problem is automatic acknowledgement by hardware on the physical layer, not the drive's address on the protocol layer.
The drive automatically pulls the DATA line low if the incoming ATN signal does not match the drive's ATNA setting.

Since the typical demo loader uses a 2bit+ATN protocol, ATN is used for clocking and is being toggled all the time. Any device on the bus not setting its ATNA value to match the incoming ATN signal in time would then invalidate what's sent on the DATA line by the current talker.

So the solution is to have a small routine running on all other drives than the one you're running the demo from, which would sample ATN and set ATNA accordingly, in a very tight loop, while it leaves the DATA and CLK lines unasserted.

(Note: 1581 ATN acknowledgement can be turned off, but 1541 and 1571 in all their variants must run software to achieve the same effect.)
2017-11-09 22:09
Monte Carlos

Registered: Jun 2004
Posts: 258
Unfortunately i did not bother very much about drive code and iec protocol and so on during my scene times. However, thank you very much for the discussion. Maybe i should have a look in the floppy chapter of my holy c64 bible.

No one who still uses a C128 dcr?
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