Discovery cartridge versions & modifications

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Fujiyama
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Discovery cartridge versions & modifications

Postby Fujiyama » Sat Oct 06, 2007 1:52 pm

I have a Discovery cartridge ("option 0" it says underneath its casing), and upon opening it up I can see that there are lots of open spaces for various ICs, connectors, switches and other components (see enclosed photo).

1) What kind of options were available for the various versions of the Discovery?
2) How about other Discovery cartridge owners with more features than mine take a photo of their circuit boards so we can compare notes. That way, perhaps those of us with less featured ones could get the parts needed to expand them?
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Postby techie_alison » Sun Oct 07, 2007 1:38 am

That one appears to be modified as the Option-0 didn't have a thru connector on it.

Attached is the circuit diagram for the HCDC. :)
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Postby atarionly » Sun Oct 07, 2007 5:09 am

If you have the software disk for the Discovery Cartridge it has all the parts listed to add the other options. Ive owner 4 of them and put all the options in except the clock. I had trouble finding one the parts.

AO

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Postby Fujiyama » Sun Oct 07, 2007 10:08 am

Thanks a million! :D
Where did you get the actual schematic? Looks like you scanned it from somewhere.
I guess it makes sense that my "option 0" didn't come with a "thru" cartridge connector, because mine is badly soldered to the board.

I never received a floppy disk, but was sent a folder full of files which is supposed to be the contents of the disk. I haven't really taken the time to look closely at those (cryptically named) files, but I'm doing that now....

DCLOCK.DOC explains how to add the clock option, but as I understand that this is just a battery-backed version of the internal Atari ST clock and not something related to the Discovery features I don't thinkl I need it (I have a MegaSTe which already has a battery-backed clock).

D128CROM.DOC which is decribed as "documentation revision 2.7" says that it describes how to modify the board so that it can accept more cartridges in the second cartridge port and how to add extra ROMs.

I haven't had the time to read through it in detail, but to me it sounds like I really need to add an extra switch, according to the docs, if I want to be able to use the "thru" connector for additional devices. So the previous owner really had no use for the cartridge connector he soldered on the board as the HART chip has to be switched off in order to access it?

I don't really understand what the ROM sockets are for. SPECTRE and Mac ROMs are mentioned, so I suppose this part of the Discovery is meant to emulate an (ancient) Mac computer?
If that's the case I don't see any need for that as I already have a (new) Mac. But if the ROM sockets can be used for other things I might be interested.
I'm also very interested in making the "thru" cartridge connector work as I need that for my project (recasing the MegaSTe which includes a chain of 3 different MIDI related cartridge devices with the Discovery at the end, and the "thru" cartridge at the very end for any additional cartridges).

If you know what the Discovery options are for, could you please summarize and explain as the documentation files I've found so far seem to go into very much detail, but doesn't explain it in general?

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Postby Greenious » Sun Oct 07, 2007 10:10 am

I got an option 2 cartridge, can make a picture of the board tomorrow and post it.

Discovery Cartridge really is ijors domain. What he doesn't know about them is probably not worth knowing anyway.
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Postby techie_alison » Sun Oct 07, 2007 4:39 pm

That is scanned in yes, it's from an A4 sheet which came with mine. If you'd like a 300dpi scan (about 800KB) then send on your email addy and I'll send you a copy.

The clock chip used on the HCDC was quite commonplace in the 80's and was made by Phillips. It's an 8573.

Given the rarity of the HCDC I'd be tempted not to modify it. I have two here and only one works.

Attached is a low res scan of both sides of the A4.
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Postby ijor » Mon Oct 08, 2007 5:59 pm

Fujiyama wrote:If you know what the Discovery options are for, could you please summarize and explain as the documentation files I've found so far seem to go into very much detail, but doesn't explain it in general?


I'm not so familiar with the extra options as I am with the basic DC functionality. But the options don't have much to do with the main DC purpose. They are there mostly because it was cheap/simple to add and because it makes (some) sense for any add-on cartridge.

As I recall the possible extras are:

- Battery backed real time clock. Not compatible with any other one. Needs its own driver.
- Cartridge pass-through connector.
- Extra drive connector and switch for using up to two additional drives.
- Eprom sockets, mainly for Magic Sac/spectre "emulation" (pirating).

The latter was very popular because the DC can read/write MAC disks, something that the original Magic Sac couldn't (not without an extra hardware add-on released later).

The option numbers represent a given combination of the above extras.

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Postby Fujiyama » Fri Oct 12, 2007 7:17 am

Greenious wrote:I got an option 2 cartridge, can make a picture of the board tomorrow and post it.


I'd love to see how you board differs from mine. Which options do you have on it?

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Postby Fujiyama » Fri Oct 12, 2007 7:21 am

ijor wrote:I'm not so familiar with the extra options as I am with the basic DC functionality. But the options don't have much to do with the main DC purpose. They are there mostly because it was cheap/simple to add and because it makes (some) sense for any add-on cartridge.


It seems that most of these options aren't of much interest for my situation/setup. The exception is the pass-through cartridge connector.
The previous owner already soldered a cartridge connector to it ("J1" on the PCB), but the documentation seems a little unclear about how this works. I believe I somehow have to modify it by cutting some traces and inserting a switch to select between "discovery cartridge mode" and "pass-through mode" (the latter in which the Discovery cartridge is disabled).

Do you (or anyone else reading) have the specifics for doing this? It's a little too easy to do something wrong when the documentation doesn't have a single drawing or schematic for this sort of thing.

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Postby Greenious » Fri Oct 12, 2007 6:17 pm

Fujiyama wrote:
Greenious wrote:I got an option 2 cartridge, can make a picture of the board tomorrow and post it.


I'd love to see how you board differs from mine. Which options do you have on it?


Sorry, been busy and forgot. Will try to get you a fancy picture or two this weekend.
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Postby Zenichiro » Fri Oct 12, 2007 7:31 pm

Sharp pics of each board revision would be very useful for the wiki. Everyone with an unmodified board please post a pic along with what options were part of that revision?

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Postby Fujiyama » Thu Oct 18, 2007 12:51 pm

Another thing....
how can I figure out if the Discovery shares the same addresses as other cartridge based devices?

I've already got a "chain" of MIDI related cartridge devices from C-Lab/Emagic (MegaSTe-Combiner-Log3-Unitor2) and want to place the Discovery at the end of the chain.

The MIDI related devices work fine (no surprise -they're meant to work together!), but the Discovery doesn't. I don't know if it's because I've had to use a cartridge extension cable making the signal prone to interference, a bad connection (the Atari cartridge connectors wouldn't be my first choice if I was to design something like this myself) or plain and simply incompatibility between the devices.

I really do need to have the Discovery in my setup, and with a permanent setup (all my cartridge devices will be soldered "hard-wired" and everything will be mounted inside a 19" rack enclosure together with the MegaSTe motherboard etc.) I simply can't remove devices.

If there is indeed incompatibility with the Discovery and the other devices, perhaps I could set up a switch which would eliminate those other devices, but I'd rather keep it simple if possible.

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Postby FujiMan » Tue Nov 06, 2007 12:08 am

FWIW, the clock chip is a Philips PCF8573.

Some 'googling' found a spec sheet. There are a few IC brokers that may have a handful of these. Dunno if 2-3 are worth a $xxx minimum order.

FujiMan

atarionly wrote:If you have the software disk for the Discovery Cartridge it has all the parts listed to add the other options. Ive owner 4 of them and put all the options in except the clock. I had trouble finding one the parts.

AO


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