EEPROM - the Holy Grail of Sideways Rom?

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1024MAK
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby 1024MAK » Tue Mar 29, 2016 10:40 am

MatGubbins wrote:not to be too chunkily soldered. :-)
Soldering is a skill that improves with practice. You don't have to use real components to practice with. Just use some thin scrap wire (telephone cable, cat5 or similar network cable etc) and solder to some strip board.
Using too much solder on a joint is a common mistake. Use the fine solder (60/40 22SWG / 0.7mm). Tin both the pin and the stripped end of the wire before trying to make a joint. What do I mean by this "tin"? It means heat up the pin or wire with the tip of the soldering iron and then apply a little solder to the point where the tip is in contact with the pin or wire, so that a small amount of solder flows over the pin or wire, but without becoming a blob. Then cut the stripped part of the wire to length. You should now be able to make a nice neat solder joint. Remember, the tip has to be in contact with both the pin and the wire, and this is the point where you feed a little more solder in.
MatGubbins wrote:- Am I right in thinking that you could avoid soldering to the bent pins at all by just snipping them off the intermediate IC socket and using test probes to connect to the pins on the EEPROM? You'd still have to solder to the switch and the test probes themselves, but even for me that bit wasn't particularly hard.
A properly made solder joint is far better electrically than a spring clip, but yes you could do it that way.
MatGubbins wrote:- I couldn't see any information/recommendation in the thread on which ROM socket to install the EEPROM in or which ROM banks it would appear as. Now having re-read this I see sydney's post on Mar 24 2014 covers this (although it superficially looks like it's relevant to a sideways RAM upgrade only).
The information is in the thread, even if it does not stand out. The thing is, as far as the CPU is concerned, sideways ROM (ROM/PROM/EPROM/EEPROM/E2PROM/Flash) and sideways RAM is all the same when it comes to the address used to access it. So what goes for one, is the same for the others (note though that this only applies for the sockets on the main board, as various third party suppliers came up with some different arrangements with sideways RAM).
MatGubbins wrote:- I tend to move my Acorn machines around a fair bit due to lack of a proper home; what are the realistic risks if one or more of the flying leads are floating around loose when the machine is turned on? My gut feeling is this is pretty safe, as the test clips I'm using are spring loaded and I think the tip would safely retract if this happened, so they wouldn't short anything out at random.
If properly clipped in, they should not come off under normal use. I am presuming that you handle your Acorn gear with care and don't do the 1 to 3 inch drop test...
MatGubbins wrote:- (I'm sure this is really really naive, please go easy on me!) Why is the 10K resistor needed on the connection to 5V? I'm looking at the BBC B circuit diagram and all sorts of pins just seem to be connected to 5V with no resistor at all. I *did* use one, but due to a quirk in how I ordered my parts I have 5 EEPROMS, 5 switches, 2 IC sockets and only one 10K resistor, so I'm wondering if I can get away without it if I want to build another one. I also find myself wondering if I could do away with the switch and just have a flying lead from EEPROM pin 27 which I connect to +5V in normal operation and to IC14 pin 1 when I want to reprogram; having to take the lid off to reprogram would be a minor hardship.
There is a good reason for using a resistor. Given that this modification is aimed at people who may not be hardware experts, it will limit the current and therefore resulting damage if the switch was wired up wrong. We do not want a high current +5V supply directly connected to RnW!
Also, this modification can be used (in theory) for other EEPROM/Flash chips, and the requirements may vary between different makes/types, so including a resistor reduces the chance of damage if the wire is connected to the wrong pin.

Mark
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby SteveF » Tue Mar 29, 2016 10:58 am

DutchAcorn wrote:Here's my implementation. The pins are bent out just enough to miss the socket.


That's very neat, and I see you have those insulating covers on the flying leads anyway. What are they called if I wanted to order some? What stops them sliding down the cable - is it just friction?

Cheers.

Steve

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Tue Mar 29, 2016 12:13 pm

Steve wrote:I hope this doesn't come across as negative...

No, not at all Steve - as far as I'm concerned, all feedback is good feedback... 8)

I think Mark has covered most of your comments except for me to say that I do wholeheartedly take on board the criticism about the absence of a summary readme or similar. I tend to develop all my projects 'live' on forum threads so that everyone can contribute and learn with me but the downside of that is the potential for scattering the key points throughout many posts. I was very lucky (even spoilt :wink: ) with UPURS for example because Paul V took over the documentation side of things and produced an excellent manual =D> - probably something that would still be absent today if it had been left up to me! My only mitigation is that I struggle time-wise to do both the hardware and software in the first place so the documentation side of things invariably tends to fall by the wayside.... :roll:

Anyway, I can only apologise to you (and indeed all those who join the party late) for the apparent lack of coherent documentation regarding the use of eeproms but I'd more than happy to take you up on your offer to produce something? If you fancy having a go, I think you'll get all the help and advice you need if you ask any questions on here :wink:

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby 1024MAK » Tue Mar 29, 2016 12:36 pm

SteveF wrote:
DutchAcorn wrote:Here's my implementation. The pins are bent out just enough to miss the socket.

That's very neat, and I see you have those insulating covers on the flying leads anyway. What are they called if I wanted to order some? What stops them sliding down the cable - is it just friction?
Hi Steve. I don't know what Paul used exactly. There are three main types of sleeving:-

(1) heat shrink - comes in many sizes and colours. You slide it on and then use hot air, a small heat gun, or a small gas torch to gently heat it up, as it warms up, it shrinks down. If you select the correct size, once shrunk, it grips really tightly, so won't pull off. Some types have a glue lining. This type is good for making waterproof joints and connections.

(2) normal PVC sleeving. Again comes in many sizes and colours. Just cut to size and slide on. The only thing that keeps it in place is friction.

(3) rubber stretch type sleeving. This type needs a three prong tool to fit it on a wire/connection. Again, comes in many sizes and a number of colours. To fit, cut to size, slide onto the tool (maybe using some special lubricant), squeeze the handle to stretch/expand the sleeve, slide over the wire/connection. Release the pressure on the tool and slide the prongs of the tool out. I hope this makes sense, it's a lot a harder to describe than do, and it takes a bit of practice to do :roll:

I hope this helps :D

Mark
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby DutchAcorn » Tue Mar 29, 2016 12:40 pm

SteveF wrote:
DutchAcorn wrote:Here's my implementation. The pins are bent out just enough to miss the socket.


That's very neat, and I see you have those insulating covers on the flying leads anyway. What are they called if I wanted to order some? What stops them sliding down the cable - is it just friction? ..

It's called heat shrink tubing. Great stuff. You may have guessed it - it shrinks on heat (hot air gun). You can get it in different diameters.

Edit: ^^ Mark provided a far more informative answer. I'll stop making short comments while at work :oops: :roll:
Paul

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby SteveF » Tue Mar 29, 2016 3:42 pm

1024MAK wrote:What do I mean by this "tin"?

Cheers Mark, I will try this next time!
1024MAK wrote:
MatGubbins wrote:- I tend to move my Acorn machines around a fair bit due to lack of a proper home; what are the realistic risks if one or more of the flying leads are floating around loose when the machine is turned on? My gut feeling is this is pretty safe, as the test clips I'm using are spring loaded and I think the tip would safely retract if this happened, so they wouldn't short anything out at random.
If properly clipped in, they should not come off under normal use. I am presuming that you handle your Acorn gear with care and don't do the 1 to 3 inch drop test...

Well not as such, but they do get picked up and put away in cupboards etc quite a bit. I will just have to see how it goes, the switch dangling out of the back should act as a reminder to check the connections when I take the machine out of storage. :-)

Thanks to everyone for all the other information too, with luck I'll make a better job of the next one I build.

I have started trying to put together a README/construction-and-use manual. I'll post a draft here as plain text later on and then maybe we can look at putting it into a word processor or something with proper formatting and ability to add diagrams later.

I've been over the thread again and I do have a few questions which I've come up with in the course of my writing:

On a B+ for a 32KB EEPROM, the connections are:
- RnW terminal on switch to IC24 pin 10
- bent up pin 22 of the EEPROM to IC24 pin 12
- bent up pin 1 of the EEPROM to pin 27 *of the socket the EEPROM is in* (so no test probe, just a bare wire end)
- bent up pin 27 of the EEPROM to the switch
- is there any particularly recommended place to pick up the 5V connection (which goes via the resistor to the switch)?

Is that right? Is there any reason to build a 16KB version for a B+, given it has 32KB sockets? (I am wondering if the advantage might be that you avoid the need to connect to pin 27 of the EEPROM's own socket, for a slightly easier build with one less wire.)

I'm trying to make the connection between the ROM socket the EEPROM is installed in and the banks at which it appears explicit in the document. I have this for the BBC B, could someone please give me a little table for the B+ showing "if you install in motherboard ROM socket ICxx, the EEPROM will appear as banks &X and &Y"?

Is it ever necessary to soft-lock the EEPROM now there's the write protect switch, on any machine? It seems to me that the soft-locking is a kind of optional belt-and-braces thing, not something you need to use to use the EEPROM reliably.

Edited to add a couple more questions:

Do I understand correctly that for an Electron with EUP board, no flying leads at all are required? You just put the EEPROM in the ROM socket with all links in the East position, then move the write protect link JP1 to the West position to prevent glitches after you've programmed it? And which banks will it appear in - 2 and 3?

(This hasn't happened to me yet, just curious!) Is there a recommended way to recover if you write a corrupt ROM image to the EEPROM which means the OS won't boot correctly? Of course you can pull the EEPROM, but if you don't have a stand-alone programmer to erase it, is there any way to put the EEPROM in write-only mode by temporarily moving one of the flying leads or something like that? Looking at the EEPROM datasheet, I wonder if connecting the flying lead from EEPROM pin 22 nOE to 5V instead of WnR would do the trick? Probably not, since it doesn't have the magic resistor. :-))

Cheers.

Steve

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Tue Jul 05, 2016 7:45 pm

Can the eeprom be placed in a rom socket on a sideways rom board like the Watford Electronics 12 Rom Board, or does it have to go into one of the motherboard rom sockets? If the latter is the case, does the eeprom still function with the Rom Board still installed?
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Tue Jul 05, 2016 8:14 pm

No, you should be able to happily plug the eeprom into any socket that supports a 'normal' sideways rom (eprom or prom) including any of the various rom extension boards provided you still perform the pin isolations and connections etc. as per the schematic previously posted. (Until I've investigated why it doesn't work [soon], ignore the Master implementation.)

:-k There is a however though - if a given rom board fully decodes all 16 roms, you are probably better to use the 16k version of the eeprom arrangement (Pin 1 of the eeprom isolated and connected to Pin 2 of the eeprom) because trying to use IC76 might conflict with what the board is doing. It would be possible to use the 32k version but the Pin 1 flying lead might need to go to Pin 20 of another vacant but decoded rom board socket. If you do want to try this 32k configuration, I need notice of the question because I'm thinking on the hoof right now.... :wink:

EEPROM fitting in Model B and Master.png

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Tue Jul 05, 2016 8:31 pm

@ SteveF - I've just noticed that you asked quite a few questions a couple of posts back (in March :shock: ) but I somehow completely missed those so may I sincerely apologise for ignoring you! #-o As soon as I get a little time (I'm drowning in projects just now :roll: ) I'll have a read and get back with some answers assuming you're still waiting.... :oops: 8)

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby SteveF » Sat Jul 09, 2016 5:26 pm

MartinB wrote:@ SteveF - I've just noticed that you asked quite a few questions a couple of posts back (in March :shock: ) but I somehow completely missed those so may I sincerely apologise for ignoring you! #-o As soon as I get a little time (I'm drowning in projects just now :roll: ) I'll have a read and get back with some answers assuming you're still waiting.... :oops: 8)

Thanks Martin, I completely understand - I've dropped out of circulation a bit myself lately anyway. When it isn't sitting in the cupboard, the EEPROM works perfectly in my BBC B, so these questions are only to help with writing up some documentation.

I've attached a *DRAFT* of what I have so far to this post, on the offchance you or anyone else would like to comment (no rush, of course). To state the obvious - DO NOT attempt to follow the instructions in this document, read the thread instead! I am not sure I've hit the right note, and I'm also a bit worried that some of the explanations I've given might be wrong...

Cheers.

Steve

eeprom-draft-2016-07-09.txt
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Sat Jul 09, 2016 7:36 pm

Wow! Looks like you've been very busy Steve...! :shock: :D =D>

I always seem to get spoilt by guardian angels when it comes to documentation for my meanderings! Paul V produced the excellent UPURS manual and I've had other members send me instructions they've written up for a few of my other projects too - I am of course duly and appropriately embarrassed.... :oops:

Anyway, thanks massively Steve - I know it's a work in progress but it's already waaay better than the info being scattered amongst the very long thread. I'll have a read in due course and see if there's anything I can add. I notice you've mentioned the Master issues and coincidentally, that's exactly what is currently under scrutiny on the bench in the Beeb vaults so hopefully I'll have something to report in the near future... [-o<

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 8:18 am

On a model b Beeb with WE 12 ROM board fitted is it possible to connect RnW to an IC other than IC14? I understand that IC14 has something to do with ram data lines, but the position of IC14 directly under the Rom board makes connecting a lead to Pin 1 rather problematic!
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby 1024MAK » Wed Jul 20, 2016 8:31 am

RnW can be picked up at any convenient place. If you study the schematic diagram, there should be other suitable places. But it has to be this control signal, not any similar but not the same named signals.

Code: Select all

RnW also shown as:
   _
(R/W)

Where the overscore is indicating the control line goes logic low for CPU write data and high for CPU read operations.

Schematic circuit diagram here :wink:

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 9:04 am

so pin 22 from IC3 perhaps?
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 10:01 am

Hmmm, so has anyone successfully got this working with a WE 12 ROM board fitted, because I've come to the conclusion it won't work. The rom board has 14L and 14H fitted with 2x8k ram to give 16k swram. I've connected pins 1&2 on the eeprom in order to try to get one extra 16k bank of ram.

I'm trying to load the ADT200 rom into the eeprom. I've placed the eeprom in socket 12 (&C) on the board. *eep16 unlock C returns Ok, but then *eeload adt200 c states EEPROM locked.

If I use the Rload command on the disk containing adt200 Rload will only load into bank 14.

So *rload adt200 8000 14 Q loads the rom into the board's swram. Hitting break then *help confirms this.

But *rload adt200 8000 12 Q also loads the rom into the board's socket 14 swram! This, coupled with the line from the rom board's manual that states "Whenever a write is made to a sideways ROM (in the region &8000 to &BFFF), it is automatically directed to socket 14 which can take RAM" makes me think the Rom Board is stopping eeload writing to the eeprom in socket 12.

/edit just to confirm, I have removed the Rom Board completely and tried the EEPROM in the m/board slots and it works fine, so I don't think it's an issue with my construction / soldering (although that is undoubtedly bad!).
Last edited by trixster on Wed Jul 20, 2016 4:18 pm, edited 2 times in total.
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby sydney » Wed Jul 20, 2016 10:09 am

I'm pretty sure the WE 12 ROM board directs all writes to it's ram socket.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 10:54 am

That's my thought too. So would shifting the EEPROM to socket 12 on the motherboard work, or is this and the other sockets disabled/bypassed by the rom board?
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Wed Jul 20, 2016 6:17 pm

I'm afraid I'm not familiar with that board and it /could/ disable the motherboard rom sockets but I'm not sure - to find out, can you move a known good rom into say the rightmost motherboard socket and see, with the WE12 board still fully fitted, if you can access that rom. (Even BASIC perhaps?) If it works, then the 28C256 eeprom will happily work there too provided we find a RnW connection for you that doesn't go via the WE board. Since the ADC chip is lifted up on top, I suggest (if your RnW wire on the eeprom is long enough), Pin 24 of the ADC which is a 2MHzE-gated RnW (nWDS) but is fine for such things as swram etc as here.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 7:05 pm

Hello Martin, thanks for your reply.

The manual for the rom board his below in case it sheds any light on the issue.

http://www.retro-kit.co.uk/user/custom/ ... s12ROM.pdf

I'm pretty sure that normal roms still work ok if placed on the motherboard as im sure i had basic and dnfs there for a bit when i first installed the rom board before moving them up onto the board itself, however I'll give Basic a go and see if it's ok.

I did try moving the eeprom to one of the motherboard slots with the rom board still in place but it still would not work unfortunately, however that was using pin 22 of IC3 for RnW, not a pin on the ADC as you suggest. I'll give that a whirl too.

Andy
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Wed Jul 20, 2016 7:23 pm

Hmmm, I wonder if the board is intercepting all the rom socket chip selects (nCS) and if a write is detected to an &8000 to &BFFF address, overriding the &FE30 rom select register setting with that of it's own slot 14. That might explain why your earlier test didn't work because IC3 Pin 22 should have been ok - I was only trying to suggest somewhere that's both suitable electrically and easily accessible with the rom board fitted. I'll have a quick look at the manual and see if the link settings make such hijacking plausible.....

Edit : Ha, yes, I think that's what they're doing so whilst the motherboard sockets will work for reads (RnW=1), they can't be selected coincident with writes (RnW=0).

There's probably work-arounds given a little thought - how keen are you to keep the WE12 and have eeprom?
Last edited by MartinB on Wed Jul 20, 2016 7:34 pm, edited 1 time in total.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 7:26 pm

That confirms what I've just tried - EEPROM on the motherboard and RnW on ADC pin 24 still unfortunately doesn't work. Bugger.

Btw, I tried removing link E-A on the board like it says "Link E to A is a push- on terminal which, when removed, protects the RAM from write operations; ie it controls write protect" but again this did not allow me to write to the EEPROM.
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Wed Jul 20, 2016 7:35 pm

I edited my previous post just as you posted....

Hmmm....the manual suggests you can set up the WE12 rom board socket 14 (H or L ?) for a 27128. If so, and you make those links as instructed in the manual, I /think/ you should be able to whack your 16k-modified eeprom in there with the flying leads as already tried. That ways, when a write occurs, which we capture with the flying lead, the socket 14 nCS which will align with the 28C256 pin when socket 14 is in a 27128-compatible config, and Bob is your uncle.... :-k

(Basically, we'd be effectively stealing the chip select back again...)

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 7:46 pm

I'm relatively keen to keep the Rom board as it gives me a straight 16k swram and a load of spare rom slots. Installed on it currently are TurboMMC, DNFS, BASIC and the OS. If there's something which might be done to get the eeprom to work in conjunction with the board then that'd be super but I appreciate it's a lot of effort to ask of you for one small user-case. I think ideally I'd like to get the board's own swram working alongside a 2x16k eeprom - i could then have one 16k bank for swapping in and out roms and one bank of 16k to supplement the board's own 16k for games like Lancelot and The Hobbit.

Andy

/edit just seen your last edit, hmmm.... very interesting, i'll give that a whirl!
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Wed Jul 20, 2016 7:55 pm

...although you'd then lose your 16k sram capability I presume because I suspect that when rom 14 is in 27128 mode, only one of the sockets, H or L, will then work. If you wanted sram too, we'd be back at square one #-o

( I'd be after ditching this write-hijacking but without a board, it'd be a painful process remotely :roll: )

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby 1024MAK » Wed Jul 20, 2016 8:00 pm

There’s always a way, it's just more a question of "how difficult" is it? :lol: And, maybe "are you willing to cut PCB tracks?".

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 8:05 pm

I think that's going to be the issue - looking at it i'm going to have to cut a track which i'm not certain is something i'm willing to do, not when i cant be certain the mod will work as we think it might. hmmmm... choices choices!
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Wed Jul 20, 2016 8:07 pm

You can try the 27128 config idea without cutting though...? There's appropriate links....?

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trixster
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 8:13 pm

MartinB wrote:...although you'd then lose your 16k sram capability I presume because I suspect that when rom 14 is in 27128 mode, only one of the sockets, H or L, will then work. If you wanted sram too, we'd be back at square one #-o

( I'd be after ditching this write-hijacking but without a board, it'd be a painful process remotely :roll: )


I could post the board to you Martin! But I suspect it's a lot of work for one small specific problem which might not be solvable!
A3020 | A3000 | BBC B + 128K RAM/ROM + 20K Shadow + Pi0 + VideoNuLA
BBC Master Turbo + DC | Atom | A1200 060 | A500 | Jaguar | A420/1
A4000/040 060 | Atari Falcon 060 | Saturn | PS1 | SNES | CPC6128 | C64 | 3DO | MD

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trixster
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Location: York

Re: EEPROM - the Holy Grail of Sideways Rom?

Postby trixster » Wed Jul 20, 2016 8:14 pm

MartinB wrote:You can try the 27128 config idea without cutting though...? There's appropriate links....?


I'm not entirely certain, but it looks like I'd have to cut a link on the board, it's not a jumper which can be removed.
A3020 | A3000 | BBC B + 128K RAM/ROM + 20K Shadow + Pi0 + VideoNuLA
BBC Master Turbo + DC | Atom | A1200 060 | A500 | Jaguar | A420/1
A4000/040 060 | Atari Falcon 060 | Saturn | PS1 | SNES | CPC6128 | C64 | 3DO | MD

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sydney
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby sydney » Wed Jul 20, 2016 8:20 pm

trixster wrote:I'm relatively keen to keep the Rom board as it gives me a straight 16k swram and a load of spare rom slots. Installed on it currently are TurboMMC, DNFS, BASIC and the OS....

I'm seriously considering taking my WE board out and replacing it with 32k ram and 3 32k eeproms, 1 holding BASIC and MMFS and the other 2 for general use. I just don't need that many roms.


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