Drive swap on STe without cutting pins/tracks

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tzok
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Drive swap on STe without cutting pins/tracks

Postby tzok » Wed Dec 27, 2017 8:42 pm

As I can't get the DIN14 plug to make my GOTEK an external drive, I have not tested presented solution, but I believe that there is a way to swap A: and B: without (well, almost) cutting and/or bending any pins. It has two variants (STe only).

* First variant is to install ID switch (1P2T) in the Atari, and in the external drive. ID0 for EPSON SMD380 is by shorting pins 14 & 15, while ID1 is by shorting pins 15 and 16. You have to enable DS0 signal for external floppy by cutting a bridge between pins 2 & 3 of W300 and connecting pin 2 of W300 with pin 1 of W301. The drawback is that you have to move 2 independent switches to swap drives A and B.

* Second variant requires only one switch in the Atari. It has to be a two circuit ON-ON switch (2P2T). One circuit switches the internal drive by shorting jumpers 14 or 16 with 15. Second circuit switches pin 2 of W301 between 1 (DS0) and 3 (DS1), effectively switching external drive between ID0 and ID1. In this case you have to cut bridge between pins 2 & 3 of W301.
Be careful and think what you're doing - it has to be a cross-switch:
- in one position internal drive is ID0 (SMD380 pins 14 & 15 shorted) and DS1 signal is routed to the external drive (W301 pins 2 & 3 shorted),
- in second switch position it should be opposite: internal FDD is ID1 (SMD380 pins 16 & 15 shorted), and DS0 (W301 pins 2 & 1 shorted) is routed to the external FDD.

Pin 1 of W30x is a square pad.

I have noticed that D0SEL signal from YM2149 also goes to the U307 (74LS244) of DMA port to create BD0SEL. If one would swap signals by YM pins 19 & 20, then effectively D1SEL would create the BD0SEL signal (which I can't find where it goes). I'm not sure which method is better (swapping signals directly by YM2149 pins or switching FDDs between ID0 and ID1).

tzok
Atari freak
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Posts: 57
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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Tue Jan 02, 2018 4:15 pm

I have tested that solution (no. 2) and I may confirm that it works flawlessly. The BD0SEL is a signal driving the FDD LED, so after swapping drives, the yellow LED indicates activity of external floppy (which is now drive A:).

The switches (TOS select and FDD swap) are mounted as follows:
Image Image

...and my external Gotek/FF looks like this:
Image Image

Dal
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Re: Drive swap on STe without cutting pins/tracks

Postby Dal » Tue Jan 02, 2018 5:09 pm

Nice solution!
Mega"SST" 12, MegaSTE, STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's

tzok
Atari freak
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Posts: 57
Joined: Fri Jun 30, 2017 7:22 pm
Location: Bielsko-Biala, PL
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Re: Drive swap on STe without cutting pins/tracks

Postby tzok » Sat Mar 03, 2018 10:01 pm

Same option is available in the STf - the jumper is marked W2, and the positions are: 2-3 = DS1->PIN5, 1-2 = DS0->PIN5.

P.S.
Currently my Gotek/HxC looks like this:
Image


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