Atari ST External Floppy Connection

[emarti]

Hi,

I am using 1040STFM. I wanna add second floppy device (Gotek). But I do not found connection wiring schema from ST to FloppyDevice. It has internal floppy device (A). My Gotek device (with FlashFloppy) is ready.

[RodLightning]

The same signal lines found in 720kb floppy cable are present in the external floppy port of Atari ST.

Info is in the manual (page 76). If I remember correctly, drive select 1 configuration is seen as drive 2, with internal being set to drive 0.

 

https://archive.org/stream/Atari_520ST_Owners_Manual_Rev._B_1985#page/n77

 

 

 

[emarti]

I am not sure but following picture may be my solution. Is this true?

 

[RodLightning]

Yes, that looks accurate. All the odd pins on the row opposite the notch are tied to ground. I built a cable years ago to connect an old double density PC 3.5 inch floppy drive to my 520STFM as drive B. I have never used a Gotek device, but if it is configured to work properly with Atari ST, it should also work as a second drive. Remember to set the drive select to 1. It would need to be set to 0 to replace the internal floppy drive.

[KLund1]

Is there any external floppy drives that can connect to a Falcon or MSTE and read/write 1.44/720/360 disks. Better yet also connect to a ST,E,F and work only 720/360

[ParanoidLittleMan]

Is there any external floppy drives that can connect to a Falcon or MSTE and read/write 1.44/720/360 disks. Better yet also connect to a ST,E,F and work only 720/360

I don't recommend to attach 360 K drive to Atari ST, Falcon, MSTE ... They can damage PSG chip (what gives drive and side selection signals) - because pull much more current on those lines than 720/1.44 drives. Talking from own experience. Only if add there line amplifiers.

[ijor]

I don't recommend to attach 360 K drive to Atari ST, Falcon, MSTE ... They can damage PSG chip (what gives drive and side selection signals) - because pull much more current on those lines than 720/1.44 drives. Talking from own experience. Only if add there line amplifiers.

 

May be you are thinking about 5.25 drives. But it seems he is talking about a 3.5 one. I think he mentions 360K for single sided 3.5 disks.

 

[ParanoidLittleMan]

 

May be you are thinking about 5.25 drives. But it seems he is talking about a 3.5 one. I think he mentions 360K for single sided 3.5 disks.

 

Right. Still, not recommended - single sided drive in 21st Century - no thanks.

[+poobah]

I don't recommend to attach 360 K drive to Atari ST, Falcon, MSTE ... They can damage PSG chip (what gives drive and side selection signals) - because pull much more current on those lines than 720/1.44 drives. Talking from own experience. Only if add there line amplifiers.

 

If it is just a signal line, put a current limit resistor on it.

[ParanoidLittleMan]

 

If it is just a signal line, put a current limit resistor on it.

Completely wrong. Putting resistors there will make it not activating drive and side selection.

I solved it btw. with adding transistors.

[+poobah]

Completely wrong. Putting resistors there will make it not activating drive and side selection.

I solved it btw. with adding transistors.

 

You know, there's difference between "may not work in this particular application" and "completely wrong".

Current limiting resistors are pretty common on signal lines.

 

The original problem as stated "...damage PSG chip (what gives drive and side selection signals) - because pull much more current on those lines"

 

True, it is possible the drive may not detect the signals, which is addressed by the solution you came up with, but the ST won't be damaged.

[ijor]

I think Pera is correct, although I agree his reply was unnecessary too harsh.

 

You need to supply that current because otherwise you might not be able to pull down the signal low enough for the drive's buffers. You need high current drivers, either discrete transistors or chips. In some cases it might be solvable at the drive's side by using weaker pullups.

 

The problem is that the original floppy "shugart" bus was specified for open collector outputs. So it was common to install very strong pullups. Worst case is connecting two (or more) old 360K drives, which obviously you won't connect to an ST.

 

Btw, a high current driver is already provided on the ST for the signals coming out of the FDC, not for the signals coming from the PSG.

[ParanoidLittleMan]

I'm sorry for writing 'harsh' - to someone who comes here with pure theory, while I wrote based on my concrete experience and solved problem.

And second post is even worse - just adding more unnecessary blah and obviously lacking experience with electronic.

It is simply that if you put small resistor it will not protect Atari, if put larger value it will not activate drive. Again: completely wrong. It is not about may it work or not. It may work, as worked for me about 1 hour. And then PSG chip broke.

And why we connected that 5.25 drive to ST ? Wanted to transfer data from it, because did not have then way to transfer it from PC. And from curiosity.

[ijor]

Worst case is connecting two (or more) old 360K drives, which obviously you won't connect to an ST.

And why we connected that 5.25 drive to ST ? Wanted to transfer data from it, because did not have then way to transfer it from PC. And from curiosity.

 

I said you won't connect two or more 360K drives, not that you won't connect one. I connected a 360K to the ST myself. There were a few third party ones specifically for the ST available at the day. They become rather popular for PC Ditto, the PC emulator. I even own one of those drives made by "IB". They even came with a boot disk to make the step rate slower, as those 40 tracks drives usually need.

 

[ParanoidLittleMan]

My talk about why connected such drive was just little history talk. Not related with your mentioning of connecting 2 5.25 inch drives. Just thought about who would need to connect it today - now data transfer is easier, but someone without PC may come to such idea ... Surely, we needed to set step rate to 12 mS - or 6 mS was good ? Kill me if I know

 

I guess you needed 360 K drive only to copy DOS. Don't see reason why could not use 3.5 inch drive for it on ST with PC Ditto.

[+poobah]

I'm sorry for writing 'harsh' - to someone who comes here with pure theory, while I wrote based on my concrete experience and solved problem.

And second post is even worse - just adding more unnecessary blah and obviously lacking experience with electronic.

It is simply that if you put small resistor it will not protect Atari, if put larger value it will not activate drive. Again: completely wrong. It is not about may it work or not. It may work, as worked for me about 1 hour. And then PSG chip broke.

And why we connected that 5.25 drive to ST ? Wanted to transfer data from it, because did not have then way to transfer it from PC. And from curiosity.

 

Sure whatever.

 

I'm glad you found a solution to your drive issue.

[+poobah]

I think Pera is correct, although I agree his reply was unnecessary too harsh.

 

You need to supply that current because otherwise you might not be able to pull down the signal low enough for the drive's buffers. You need high current drivers, either discrete transistors or chips. In some cases it might be solvable at the drive's side by using weaker pullups.

 

The problem is that the original floppy "shugart" bus was specified for open collector outputs. So it was common to install very strong pullups. Worst case is connecting two (or more) old 360K drives, which obviously you won't connect to an ST.

 

Btw, a high current driver is already provided on the ST for the signals coming out of the FDC, not for the signals coming from the PSG.

 

Yes, if the drive needs all the current, it won't work, but the computer won't be damaged, that's all i was saying.

Strange to put drivers on some signals but not others.

[ijor]

I guess you needed 360 K drive only to copy DOS. Don't see reason why could not use 3.5 inch drive for it on ST with PC Ditto.

You could, of course, use 3.5 disks, but you needed the 5.25 drive to access any 5.25 PC disk, not just DOS. Sometimes you actually didn't need it for DOS, because some versions of DOS came with 720K disks (PC DOS 3.1, IIRC). But you might have your own PC data disks on 5.25.

[ParanoidLittleMan]

Here is how I done it 31 years ago:

4 transistors + 2 resistors.Really cheap and 10 minutes work. Could do with 7407 too, I guess.

 

"Strange to put drivers on some signals but not others." - WD1772 signals all go via inverters, so driver is a must. Maybe it's designers intentionally made it so, to force computer designers to add drivers. PSG signals are OK for 3.5 inch drives. I don't blame Atari for this - nobody said that it will work with 5.25 drives without problems.

[David Hefner]

To the OP: You could always mount a gotek internally like I did. Works great, no issues so far at all (I have about 10 hours or so on it).