Updated "ROM-Scanners" and the like.

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sun Jan 10, 2021 12:41 am

It's been quite a while since the two versions of the "ROM-scanners" were published by Ralph Taggart and Klaas Robers. Things in terms of non-volatile memory have moved on greatly since then. I'm looking ahead once the NBTV/SSTV-625 up-convertor is completed to possibly my next project.

It's basically the same concept but brought up-to-date, no EPROMs, but using Flash memory allowing much greater storage and no UV erasure boxes which would require a total reprogramming of the memory...and no 12.5V-25V programming voltages required. Instead using Flash memory which would allow a replacement of a single image if desired. Plus the amount of storage is vast compared to EPROMs as well as being only 8-pin instead of 28-pin plus.

Image below shows a size comparison even though not the devices in question. The small device is SOIC, more correctly called SOIJ these days and is perfectly hand-solderable.

DIL 28-pin EPROM 2.jpg


The small device is a 64Mb (64mega-bit or 8mega-byte) Flash non-volatile memory device which costs GBP about 2.50 or US$3.50. (Size corrected 10/01/21).

Now, the reason I mention this at this stage is what would you guys like in terms of functionality/features? Simple programming from a USB port is an obvious one. An animation sequence is another, possibly with sound, others?

This could also be applied to SSTV as well.

Steve A

An alternative is a USB Flash-drive/memory-stick, but if you've even just glanced at the protocol required for USB you'll realise it's beyond mere mortals, OK, it's beyond me! Though I have dabbled with SD cards in the past and they are a possibility...aside from the initial configuration they're not vastly different to the Flash memory above. If you have a few SD cards of 2GB or less kicking around in the dust at the bottom of a drawer, hang on to them. It's probably wise to check they still work as they'll be quite some years old by now.
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Updated "ROM-Scanners" and the like.

Postby acl » Sun Jan 10, 2021 9:20 pm

Looks like a good Idea,

Graham Lewis did produce one with NBTV pictures immedded in a PIC and used an analogue input to change pictures. I was impressed with Andrews method of using a SD card to store images. One Idea would be to produce a convertor to compliment the NBTV/SSTV/ to 625 line convertor with one that produced SSTV/NBTV signals selectable from either a PAL camera or JPG images stored on a SD card. The unit would have a reader and CCIR signal input.

Regards Chris
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Sun Jan 10, 2021 11:05 pm

Some years ago I did a Photo-to-SSTV device but I've never published it. I used it to generate the pictures shown in the MkI up-converter examples. It was a bit labour intensive requiring several manual steps to achieve the SSTV output. One day I should re-visit it. Though decompressing a JPEG might be quite a challenge.

I think somewhere lost in time I did make a start on 625-SSTV, but using the cheap cameras usually available the results were somewhat disappointing. And seeing that SSTV is really a sequence of stills there didn't seem any point so I took it no further.

But certainly a monochrome TIFF or BMP to SSTV is entirely possible...as noted above, I've done it before. It just needs some automation thrown at it!

Steve A.
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Re: Updated "ROM-Scanners" and the like.

Postby Harry Dalek » Mon Jan 11, 2021 3:11 pm

I a total dummy on these things ,i don't know how this relates to your other project so i googled what the hell are these things ! ; )
Got this
Read-only memory is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device.
So i think it means you use this to program the rom and its stuck in there for good ?
BIt like a 2021 version a record !
Do take it Steve that some of us have less brain cells to work with think i need some Rom's in my head ! 8)
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Mon Jan 11, 2021 5:06 pm

The original (and now very old) EPROMs (Erasable Programmable Read-Only Memory) had a quartz window in the case/package. (Photo follows). You programmed them from a blank device using a 12.5-25V supply on one pin and using an EPROM programmer. If you wanted to change/update the contents you had to expose the quartz window to quite a high dose of UV light for 15-20 minutes. Then program it all again...
DIL 28-pin EPROM 1.jpg
DIL 28-pin EPROM 1.jpg (37.57 KiB) Viewed 110 times


EPROM UV erasure.jpg
EPROM UV erasure.jpg (32.23 KiB) Viewed 110 times


You put the devices to be erased in the front drawer, set the timer........and waited....some even made a 'ding' sound, much like an egg-timer, to let you know it was 'cooked'!

Once programmed you covered the window with some sticky opaque tape, otherwise sunlight with its UV content would slowly (weeks/months) erase the device. Maybe not much of a problem in the UK!

Then came EEPROMs, (Electrically Erasable Programmable Read Only Memory). Same idea, but now no Quartz window, no high voltage required, no UV erasure box, and took less than a second to erase the device. They're still made and available but they are nearing their twilight years, Flash memory is flavour of the month currently. It's what's used in the micros for various projects here as well as your USB Flash-Drives.

Imagine having to wait 15-20 minutes to erase a USB drive, where everything on it is deleted, no way to just delete one file...then put them all back?

Steve A.
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Re: Updated "ROM-Scanners" and the like.

Postby Harry Dalek » Mon Jan 11, 2021 5:26 pm

I have a fair few of the EPROM with uv window ,i sort of knew they get wiped via uV light window...i don't think you would need a device you could do it passive way the sun is a UV monster leave it in day light for a bit .
Yes all these form of memory are confusing for those that never tried them and even more so how to use them .
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Mon Jan 11, 2021 5:32 pm

I mentioned before, I used to have bucket-loads of them, but as time went on I realised they were as good as useless...so in the bin they went. That was probably 25 years ago!

Going back to your posting, there are 'One-Time Prorammable' versions. Exactly the same as the EPROMs mentioned above, but no quartz window, once programmed there's no way to erase them. Once you have proven code and a marketable device/product you should never need to change the code. So these devices were used in mass production. The absence of the quartz window made them far cheaper for manufacturers, it was quite an expensive operation to include it...and of course the devices didn't self-erase when exposed to sunlight.

"I'm sorry sir, we cannot update the software with the devices fitted in your version. You'll have to buy a new one," Me? Cynical? Nah!

Thankfully I think those days are gone...

Steve A.
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Re: Updated "ROM-Scanners" and the like.

Postby Harry Dalek » Mon Jan 11, 2021 5:55 pm

Steve Anderson wrote:I mentioned before, I used to have bucket-loads of them, but as time went on I realised they were as good as useless...so in the bin they went. That was probably 25 years ago!

Going back to your posting, there are 'One-Time Prorammable' versions. Exactly the same as the EPROMs mentioned above, but no quartz window, once programmed there's no way to erase them. Once you have proven code and a marketable device/product you should never need to change the code. So these devices were used in mass production. The absence of the quartz window made them far cheaper for manufacturers, it was quite an expensive operation to include it...and of course the devices didn't self-erase when exposed to sunlight.

Steve A.


I think i like the idea fixing a mistake with the reprogrammable versions pity they are not drop in copies good to experiment till you got it right ,what do you do in this case as in testing that the programming it correct ? if it can only be written to the ic before testing you would have to buy a few just in case ....speculating !
I am a hoarder :roll: can't bring my self to chuck those ics in the bin its always just in case you better not :oops:
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Re: Updated "ROM-Scanners" and the like.

Postby Steve Anderson » Mon Jan 11, 2021 6:11 pm

Harry Dalek wrote:I am a hoarder :roll: can't bring my self to chuck those ics in the bin its always just in case you better not :oops:

OK, a couple of questions...have you got a UV eraser? Have you got an EPROM programmer? Do you want to spend money or barter/trade them with something? There'll be many gathering dust on peoples shelves for sure. A lot of the hobbyist versions required something like a BBC-B computer to interface to. Though RS232 versions with DOS based software were the majority...

And of course you're limited by the small amount of memory EPROMs possess. I can't imagine anyone proposing using EPROMs these days, but possibly someone might...they're also quite slow compared to current memory chips...

I'm not putting a 'downer' on them. they were good in their time, but honestly that time has long passed..

Steve A.

It raises an interesting question. I'm interested in valve/tube technology, it's so different to Silicon. Will anyone, say in 30 years time, look at EPROMs the same way? The problem is what will be different in 30 years time? One heck of a lot for sure...but I doubt I'll be around to witness it!
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Re: Updated "ROM-Scanners" and the like.

Postby Harry Dalek » Mon Jan 11, 2021 8:07 pm

Steve Anderson wrote:
Harry Dalek wrote:I am a hoarder :roll: can't bring my self to chuck those ics in the bin its always just in case you better not :oops:

OK, a couple of questions...have you got a UV eraser? Have you got an EPROM programmer? Do you want to spend money or barter/trade them with something? There'll be many gathering dust on peoples shelves for sure. A lot of the hobbyist versions required something like a BBC-B computer to interface to. Though RS232 versions with DOS based software were the majority...

And of course you're limited by the small amount of memory EPROMs possess. I can't imagine anyone proposing using EPROMs these days, but possibly someone might...they're also quite slow compared to current memory chips...

I'm not putting a 'downer' on them. they were good in their time, but honestly that time has long passed..

Steve A.

It raises an interesting question. I'm interested in valve/tube technology, it's so different to Silicon. Will anyone, say in 30 years time, look at EPROMs the same way? The problem is what will be different in 30 years time? One heck of a lot for sure...but I doubt I'll be around to witness it!


NO i think the reason i kept them was i read some where in one of the news letters years back there was talk of using them as alight pickup so nothing to do with what they are used for i was thinking i might try that out .
Yes having little memory is a big problem i suppose there might be some people out there that collect old parts like this ,no big problem it's the first i have remembered here i have them .
When i moved to Melbourne in 2000 i left behind some CRT's i always regretted ..i agree those vacuum Tubes are still well worth keeping and will out live as a wanted item see the prices these days for them ...they are just so interesting and they glow ! does it get any better !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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