My new baby!

[1024MAK]

Oi! No poking at the back!

Keep it coming Mr C. We like updates

Mark

[sirmorris]

I was just about to press the button on the board making process when I had a thought. I thought about having EEPROM programmable by the zeddy and having a 16K extended ROM with new commands and stuff so I just had to have a play. I hate it when that happens.

The good news is: with a little fettle I have 16 ROM working. So extended BASIC is a possibility. Also the pinout on the ROM socket should support 16k of EEPROM but I haven't tested that yet, not having a 16k EEPROM to hand. But it should work, given the technology's heritage. (Not many people know that with a little soldering and a new GAL ZXpand classic can program EEPROMS in place - although had they read these forums more closerer they would have done..!)

The bad news is: NOTHING! THERE IS NO BAD NEWS!!

So with this thought train's more troubling aspects asuaged, I can proceed to ordering tomorrow without further board mods. Boom!

[Paul]

Hi Charlie,
I'm feature creeping again
I always use the w27c512 which has 64KBytes and are cheap to buy and have EPROM pinout, so direct replacement with a 27C128, about 50ct each and could keep several configurations (SWITCHABLE!).
It would be good to be able to switch configurations. Like using a 16K ROM like Sponzy, or your new enhanced basic, or your old switching 8K variant.
Please keep in mind that we NEED the option to have RAM at 8-16K area as many use your ZXPand in combination with Zeddynet (still few available ).
And we could use a litte more RAM. There are 64K versions of your thin RAM chips as well like UM61512AK-15.
Having 64K would trigger owners of the obsolete ZXPand to buy a new one .
By the way, if we had 64K RAM we could load alternative ROM images from SD to RAM and execute them from there

[siggi]

And we could use a litte more RAM. There are 64K versions of your thin RAM chips as well like UM61512AK-15.
Having 64K would trigger owners of the obsolete ZXPand to buy a new one .

64 K ram would also allow to run "bigger" ZeddyNet applications like "NFM" ("Network Filemanager" to load/save files via ZeddyNet on a TNFS-Fileserver, running on your local PC or somewhere in the internet). NFM is 16K in size and runs above 32K, using the ZeddyNet-Systemvariables located at 8K (thus needs ram in range 8K to 48K).

Siggi

NFM: http://forum.tlienhard.com/phpBB3/viewt ... 866#p21866

[sirmorris]

BOARDS ORDERED

Boardered?

[Moggy]

Excellent news good sir knight,your hard work now come to fruition(Still purple with the megawatt LED's I hope?).


Dashes off to write another song in Charlie's honour,this time in MIDI.
Now where did I put that interface?

[sirmorris]

I always use the w27c512

yes, I took your recommendation

It would be good to be able to switch configurations.

Agreed. I have put a 3-way solder jumper on the A14 line which can have a switch added for the cases where banked switching of ROMs is required.

Like using a 16K ROM like Sponzy, or your new enhanced basic, or your old switching 8K variant.

Yes, this was something I tried yesterday. Even in its rough state you can have either a 16K ROM or 8K ROM and RAM. Some hires programs require the RAM at 8K too.

And we could use a litte more RAM.

I considered this but for most users 64k RAM is not necessary, and to be of any use the user would have to modify their zeddy to implement some kind of m1-not circuit. Additional ROMs would only work if ZXpand had a split bus, as the character generator can only access font data in the internal ROM.

I want to keep ZXpand a plug-and-play, simple and bullet-proof solution for every-day use. There are other devices available - such as More & Blast - which can satisfy the more adventurous users

[Moggy]

I always use the w27c512

....I want to keep ZXpand a plug-and-play, simple and bullet-proof solution for every-day use. There are other devices available - such as More & Blast - which can satisfy the more adventurous users

HEAR HEAR!

I remember this was your remit way back in 2007 when the spand was a piece of Veroboard in a Sinclair ram-pack. Glad you stayed true to this same remit.

[Paul]

Additional ROMs would only work if ZXpand had a split bus, as the character generator can only access font data in the internal ROM.

The "only" thing you need to do is activate the ROM whenever it's content is needed.
Sounds easy, doesn't it? You already realized part of it in your ZXPand, the part that gives data on Memory request.
If you want to give the character data to the databus you need to activate the ROM on refresh at the right moment (whenever the ULA would activate it). The problem here is that you cannot (easily) pull /ROMCS high to deactivate the internal ROM AND see when the ULA drives this low to activate the ROM. But there is also a solution to this:
Do the same as the ULA does in your CPLD. In other words, count the lines to know when which row of the characterset is requested and activate the corresponding part of the ROM (I guess these few adress lines are meant with split bus?) and reset the line counter whenever the ULA does reset its line counter.
It's as simple as that. Have a closer look AFTER you finished the MIDI MIDI MIDI MIDI MIDI MIDI MIDI interface.
Kind regards
Paul

[Moggy]

It's as simple as that. Have a closer look AFTER you finished the MIDI MIDI MIDI MIDI MIDI MIDI MIDI interface.
Kind regards
Paul

Große Köpfe denken das gleiche.(I think this translates ok)