4xTOS selection for STE?

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simonsunnyboy
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4xTOS selection for STE?

Post by simonsunnyboy »

CLOUDY requiring the Lightning ST, I wonder what options are available to implement a clean switchable TOS for STE ?

I would love to be able to switch between 4 256K images (1.06, 1.62 206 and EmuTOS) in my STE with hardware switches.

Adrian Black did something like a switcher for a C64 KERNAL where basically a switch controls additional chip selects and address lines to a larger ROM chip. See https://www.youtube.com/watch?v=GPq5xnJRw2w

For a rough reproduction on the STE, basic ingredients would be 1MB FLASH with parallel data bus, some sockets with wiring to get in the existing TOS sockets and a logic to select which 256K chunk of the FLASH is visibile to the STE in the end.

Any selector should be designed to only select lines at cold boot so it is not possible to select another ROM while the machine is powered on.
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Re: 4xTOS selection for STE?

Post by czietz »

If you do not want to re-flash the TOS versions later, the minimum solution would be to put some programmed SST39SF040 flash ICs into the sockets in the STE, bend up the pins for the two top address lines and connect them to two toggle switches. Obviously, then you have to take care yourself not to switch TOS while the machine is on.
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Re: 4xTOS selection for STE?

Post by tzok »

Same as with 2 TOSes and 1 switch, but you'll have 2 switches then. You may also use a binary encoded 4-position rotary switch. JEDEC compatible EPROMs were made up to 8 Mbits... one set of STe ROMs is 2x 1 Mbit.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

I would probably use some Arduino or Attiny device for the bank decoding like Adrian did.
2x SST39SF04 with 512K according to https://www.microchip.com/wwwproducts/en/SST39SF040 should do the trick.

that part here would be right? https://www.reichelt.de/multi-nor-flash ... stct=pos_3

But I have no idea how to get the correct decoding lines for the address and chip select from the TOS sockets in the STE to route to the FLASH chips :(
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Re: 4xTOS selection for STE?

Post by czietz »

simonsunnyboy wrote: But I have no idea how to get the correct decoding lines for the address and chip select from the TOS sockets in the STE to route to the FLASH chips :(
I'm not sure I understand your question. Simply put them into the sockets. Be sure to jumper (W102-W104) the STE mainboard to 27C1001 configuration. Bend up pins 1 (A18) and 30 (A17) of the flash ICs and connect them to switches or your selection circuit.
Last edited by czietz on Sat Dec 07, 2019 1:12 pm, edited 1 time in total.
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Re: 4xTOS selection for STE?

Post by Arne »

simonsunnyboy wrote:I would love to be able to switch between 4 256K images (1.06, 1.62 206 and EmuTOS) in my STE with hardware switches.
Do you want to use pre-programmed FlashMemories or do you want to flash them while inserted in the STE?
simonsunnyboy wrote:Any selector should be designed to only select lines at cold boot so it is not possible to select another ROM while the machine is powered on.
Tricky. Especially cold-boot. Any circuit could latch the selection lines while /RESET is active, but this is not cold-boot by default.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

czietz wrote:
simonsunnyboy wrote: But I have no idea how to get the correct decoding lines for the address and chip select from the TOS sockets in the STE to route to the FLASH chips :(
I'm not sure I understand your question. Simply put them into the sockets. Be sure to jumper (W102-W104) the STE mainboard to 27C1001 configuration. Bend up pins 1 (A18) and 30 (A17) of the flash ICs and connect them to switches or your selection circuit.
For you it might be that easy indeed. This is something I would definitly prefer to do together with someone who knows what's going on.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

Arne wrote:
simonsunnyboy wrote:I would love to be able to switch between 4 256K images (1.06, 1.62 206 and EmuTOS) in my STE with hardware switches.
Do you want to use pre-programmed FlashMemories or do you want to flash them while inserted in the STE?
simonsunnyboy wrote:Any selector should be designed to only select lines at cold boot so it is not possible to select another ROM while the machine is powered on.
Tricky. Especially cold-boot. Any circuit could latch the selection lines while /RESET is active, but this is not cold-boot by default.
I would probably preprogram the two chips first. In-circruit reprogramming would not be a target if I am in charge.

Handling the latching, I think Adrain Black's switcher keeps RESET active until his select lines are powered. I guess something like this would be necessary here.

If all fails, a set of plain toggle switches would be ok aswell. My Amiga 500 has this for Kickstart switch aswell. I am pretty sure that one has no extra circuit installed and toggling the switch while the machine is powered up may crash the machine.

All in all why I ask for existing solutions as whate ever I would come up with would be rather hacky....
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Re: 4xTOS selection for STE?

Post by kodak80 »

Quad TOS ROMs are covered here: http://www.tehkella.net/retro/?p=257
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Re: 4xTOS selection for STE?

Post by tzok »

Software switching could be tricky, as there is a risk, that Atari would boot faster, than your uC based switcher. The ROM switching thingy would need to ensure, that reset line is held low on power up until the switcher firmware boots up. Another trick would be to keep keyboard working while computer is in reset state (as I guess you'd like to switch ROM banks from keyboard). By default IKBD is reseted together with the main CPU, and there is no easy way to read keys without the IKBD being live.

I can see one solution - your ROM switcher monitors the keyboard, and when detects a right combination it pulls the reset line low and while holding it low changes the ROM select lines (2 highest ROM address lines). On power on it should boot the default ROM. On AVR, after power-on, most GPIO lines are Hi-Z, so add external pull-ups and you'll have Hi, so your default ROM is the last one.

Anyways - I think toggle switches are much simpler and reliable solution.
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Re: 4xTOS selection for STE?

Post by Arne »

tzok wrote:I can see one solution - your ROM switcher monitors the keyboard, and when detects a right combination it pulls the reset line low and while holding it low changes the ROM select lines (2 highest ROM address lines). On power on it should boot the default ROM. On AVR, after power-on, most GPIO lines are Hi-Z, so add external pull-ups and you'll have Hi, so your default ROM is the last one.

Anyways - I think toggle switches are much simpler and reliable solution.
Sorry, but I can't see your point. I'm using an ATtiny for selecting the TOS Slot in Flash (1040STFM) - works reliably. During selection /RESET is still high. My PCB is designed to run in conjunction with some other hardware extension but in general it should work as a stand-alone solution (ATtiny SW adapted).
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

kodak80 wrote:Quad TOS ROMs are covered here: http://www.tehkella.net/retro/?p=257
That is basically a more elaborate description of czietz's original proposal. I am pretty sure the FLASH chips he mentioned are dropins for the EPROM mentioned at that URL, both are 32pin DIL and both have 512K capacity.

It still indicates a lot more modifications on the mainboard that I can handle alone.

Thanks for mentioning though!
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Re: 4xTOS selection for STE?

Post by czietz »

Note that the 27C040 EPROMs mentioned in kodak80's link and the SST39SF040 flash ROMs that we talked about have slightly different pinouts. That's why I mentioned which pins you have to bend up.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

czietz wrote:Note that the 27C040 EPROMs mentioned in kodak80's link and the SST39SF040 flash ROMs that we talked about have slightly different pinouts. That's why I mentioned which pins you have to bend up.
Thanks for mentioning this.

I assumed I could in theory directly replace the chips with the fkash based ones
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Re: 4xTOS selection for STE?

Post by tzok »

39SF040 Flash has the same pinout as the 29C040/29F040:
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Source: http://romlaboratory.dbwbp.com/romlab/cart2epr.htm

Up to 2 Mbit there is no difference in pinout between EPROM and Flash.
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Re: 4xTOS selection for STE?

Post by tzok »

Arne wrote:Sorry, but I can't see your point. I'm using an ATtiny for selecting the TOS Slot in Flash (1040STFM) - works reliably. During selection /RESET is still high.
If you use "pure" uC, then it has chance to work, but if you use something like Arduino, it's bootloader may wait longer than power on reset on Atari ST lasts.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

tzok wrote:
Arne wrote:Sorry, but I can't see your point. I'm using an ATtiny for selecting the TOS Slot in Flash (1040STFM) - works reliably. During selection /RESET is still high.
If you use "pure" uC, then it has chance to work, but if you use something like Arduino, it's bootloader may wait longer than power on reset on Atari ST lasts.
The reset signal in such solutions is directly controlled by the uC or Arduino so it doesn't matter.
Watch Adrian's video, he explains this well, and Arne showed me his design which does something similar with a bare uC.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

simonsunnyboy wrote:
tzok wrote:
Arne wrote:Sorry, but I can't see your point. I'm using an ATtiny for selecting the TOS Slot in Flash (1040STFM) - works reliably. During selection /RESET is still high.
If you use "pure" uC, then it has chance to work, but if you use something like Arduino, it's bootloader may wait longer than power on reset on Atari ST lasts.
The reset signal in such solutions is directly controlled by the uC or Arduino so it doesn't matter. It is routed through and controlled accordingly with any time necessary.

Watch Adrian's video, he explains this well, and Arne showed me his design which does something similar with a bare uC.
Simon Sunnyboy/Paradize - http://paradize.atari.org/

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Re: 4xTOS selection for STE?

Post by tzok »

I've seen the Adrian's video, but my consideration was only the initial state after powering on, not the consecutive switchings.

All the required signals on STe you can find on the keyboard connector (including the floppy LED, and the /RESET signal). The drawback is - on ST there is no easy way for reading actual key presses, you are limited to reading scancodes over the serial link. The only "key" you could actually read directly is... RESET. So instead of driving the /RESET line, you could actually do the switching while RESET is pressed long enough.
Last edited by tzok on Sun Dec 08, 2019 1:11 pm, edited 1 time in total.
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Re: 4xTOS selection for STE?

Post by simonsunnyboy »

I never intended to read an actual keyboard key but a hardwired switch or button.
Arne's solution listens to the IKBD TX if I understood correctly.
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