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Old 13th May 2021, 3:07 pm   #741
ortek_service
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Default Re: MK14 schematic revisions

Quote:
Originally Posted by Mark1960 View Post
Quote:
Originally Posted by DeltaAlpha52 View Post
My current setup uses a bigger display but on a veroboard and is a bit messy
What display type did you use? Do you have a schematic or sketch of connections?
Looking at those pictures Timbucus attached a few posts ago back in Jan, the trev_ham ones used 2off 4 digit (12 pin) modules. So using these means a lot-less PCB tracking than individual digit ones, so should be feasible to wirte-up on some matrix-board with just 12-wires from each to the connector. Or design a small PCB, without too much trouble.

I could just about read the display's part-numbers, and found datasheets on these (and some being sold on alibaba for $0.30 each at 100off):

0.28" 2481AS https://www.oasistek.com/pdf/TOF-2481AS-1N.pdf
- These ones show centre-Colons, but above datasheet doesn't show any connection for these!

and

0.36" 3641AS: https://www.tme.eu/Document/080bc430...641AUHR-21.pdf


Looking on one of the datasheets, it seems the 'S' suffix is for Hi-Intensity Red - So should be more efficient / brighter than original standard Red.
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Old 13th May 2021, 9:29 pm   #742
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Default Re: MK14 schematic revisions

I ordered 10 off the 2481AS, 0.28” with my last order from Utsource. Confirmed these are common cathode and light up very clearly using my multimeter on 200 ohm range so probably no problem driving from MK14. May even be worth including series resistors to drop the current a bit. These don’t have the centre colon.

I also ordered 10 off 4 digit 0.56”, but ordered common anode by mistake, these are maybe a bit large for the MK14 but still very clear and uniform illumination with the multimeter.

These 4 digit displays seem very common, hopefully they are all using a common pinout, but I would probably buzz out the connections using a sample of the ones I have.

I also have a set of 20 single digit 0.28” from ebay from when I ordered the bubble display from russia, but these are also common anode and a strange QIL type pin arrangement that doesn’t fit a 0.1” matrix. Also common anode.

I’ve tried finding seven segment displays to fit a 50mm wide window case, but only the bubble displays seem to be small enough and I wanted to use something easier to source. This was for a PIC14, so still looking for a suitable case to use two four digit displays.
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Old 1st Oct 2021, 9:37 am   #743
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Default Re: MK14 schematic revisions

DeltaAlpha52 (Dave) contacted Trevor H to see if he still had any of his MK14 display PCBs avaliable, he doesn't but was kind enough to pass on the Gerbers so we could get some made. He was also happy for the files to be made avaliable here (attached).

I have had some boards made and have 3 spare which I can pass on to forum members, PM me with your address and I'll pop them in the in the post.

Chris
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File Type: zip Gerber_LED_DISPLAY_PCB_2021-08-30.zip (6.9 KB, 68 views)
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Old 1st Oct 2021, 10:30 am   #744
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Default Re: MK14 schematic revisions

Thanks for that information and thanks to Trevor H for kindly making his source files available.

Briefly OT, is Owen [Ortek_Service] OK? We haven't seen him here for a while.
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Old 1st Oct 2021, 11:18 am   #745
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Default Re: MK14 schematic revisions

Yes Owen is still around, saw him yesterday !
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Old 2nd Oct 2021, 1:50 am   #746
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Default Re: MK14 schematic revisions

Yes, thanks for asking SiriusHardware, I'm still around (And surprised this thread is, with many months gaps until now) !
- I've just been too busy to really even look on here, since now being out all day at work again for the last few months (although the vintage computers area it did seem to have gone fairly quiet).

Also a bit OT, but:
It seems in the meantime, the site doesn't like my old retro Win-XP PC anymore, as I was getting unsupported SSL protocol messages on Chrome, that used to work and AVG complaining about out of date certificates. Although since a reboot (after a badly-timed 1s power-cut around here - the first complete dropout for ages) I just get Chrome complaining my PC clock is ahead (which it isn't) so certificates don't work.
Luckily Firefox (with it's own more recent SSL protocols, not relying on the OS's ones that MS never updated) still works
- So I haven't had to endure Win10 that I recently got on a v.cheap Laptop (from going to first Radio Rally since Mar'20!), that has been useful on other website that won't function anymore on older browsers.


Back to MK14 matters, although I did get one of the Russian original-display type equivalents from there, via an online marketplace, it did seem a bit small to want to work with too-much these days. So I think I'd like to try something a bit larger, similar to ones mentioned previously

I just need to finish-off a few bits on assembly of PCB I got from ChrisOddy that I've not had chance to recently. Mainly needing the getting more difficult / expensive to buy SRAM's. So I was looking to improvise something with much more available 2114's, that I'd acquired lots of, until I possibly find some of the correct ones amongst some old computer boards etc. I've got (I've still not found where my Dataman Microdoctor is, to get internal photos of)

Plus need to get some Tesla-PROM's now stocks of the NS ones have seemingly all been depleted - ChrisOddy is now able to program Tesla-PROM's (on an Acorn System at least, with a modified version of it's original PROM+EPROM programmer) after working-out how best to program these
So don't an expensive Elnec-design (Dataman-Pro) etc. programmer (Although having access to one came in handy, in working-out the voltages and timings, as Tesla data / translation of it was rather unclear).

Hopefully I'll be back a bit sooner to looking at these and the forums.....
Owen
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Old 2nd Oct 2021, 8:44 am   #747
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Default Re: MK14 schematic revisions

OK Owen, glad to hear from you - we feel nervous about anyone who goes missing in these troubled times. All general points noted, though I'll treat those as read-only to avoid taking the thread further off topic. It has evolved into our 'Anything generally to do with the MK14' thread, so it's good if it gets a nudge every now and again.

I don't mind the small displays as they were what went with the territory, but it was generous indeed of Trevor to make the design files for his larger substitute displays available.

I've suggested in the past that any future revisions of MK14 replicas should, instead of using the 2111 / 9111, be re-pinned for the 2114s which are reasonable lookalikes and much more widely available, even if the extra 3/4K capacity in each chip is just wasted. If the form factor is not regarded as critical then better still, move to a 62256 RAM and a conventional wide bodied EPROM. It wouldn't much resemble an original MK14 but it would 'drive' exactly the same. Taking this concept to its ultimate conclusion you end up with MK14man's noughties redesign of the machine, but I think the use of mid-period 'conventional' DIP hardware makes it more accessible to more people.

I acquired a small stash of Philips / Signetics N82S131Ns which also work well as 74S571 replacements so my PROMly needs are met for the moment. I do believe Slothie has a programmer for the Tesla MH74S571 on his conveyor belt, it may even be at the PCB design stage. Of course the more people who become able to programme those devices, the more valuable it becomes. The main reason they were so cheap in the past was that virtually no-one could programme them. If people suddenly start wanting them then woosh, up the price will go.
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Old 2nd Oct 2021, 6:07 pm   #748
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Default Re: MK14 schematic revisions

Yes, ChrisOddy has also been trying to contact the person who had unearthed some Softy-2's and their documentation a few months ago but we haven't heard from since. So hopefully OK as well.


I'm finally back on here using my favourite Chrome under XP, after many hours of Googling and trying to understand web security protocol certificates etc.! - I discovered a web 'R3' certificate expired on 30th Sept, so I had the same problem on many websites, even though they should be sending out the 'new' ISRG Root X1 replacement and PC updating to this automatically.

I did finally manage, to add TLS 1.2 & 1.2 to original XP OS, after looking in the past a bit but now finding some instructions from a couple of years ago on how to get use the XP POSReady updates and do some registry hacks to make this work, inc. on IE8. I thought this would help with SSL protocol issues, but it didn't solve the recent problem, and I couldn't seem to find the ISRG Root X1 as a .crt file, to add manually. But after removing all out of date certificates, Chrome is now suddenly now working OK on most affected websites (Although strangely not https://letsencrypt.org/ yet, that seems to be main host for these!)


Back to the MK14, I did a while ago plan to make converter boards (just a veroboard etc. prototype to start with), to allow use of 2114's - Although original layout of the MK14, does mean it's easier / neater to do with separate boards, rather than one larger one to plug in everywhere.
And had a cunning plan to fill-in the memory-map official expansion area spaces (when fuller address-decoding is implemented), as I hate to see the extra memory wasted! - I seem to recall being able to do most of this with only the odd extra gate, due to fortunate just inversion of an address line for most of this - rather than a complex PAL / PROM address decoder etc. being required.

There were 0.3" wide DIL versions of the 62256 etc, often for old PC cache, that might be easier to fit in than the wider one. But I've not seen any small than SO28W in surface-mount to make a same size drop-in DIL replacement module, you could make look like the original IC with some 3D printing of covers etc if required. And Chip-Scale Packages for anthing more recent, wouldn't be too easy to assembly at home for most!


The NS PROM's weren't actually too badly priced from Australian stockist, (as were Futurlec in USA etc) before they sold out. So it's more of a problem that there's not going to be many people with a significant stash of these - And unlike all the other IC's, used ones aren't too much use! (unless they happen to have been programmed with the program you want)
And I suspect that even Tesla stopped making these decades ago, so it's a case of limited stock NOS devices - And 'panic-buying' mayl just affect availability in the long-term if people hoard them, rather than the price (unless people 'invest' in buying-up and reselling these (as I suspect some Far-East etc. companies may be doing with cleaned-out UK/US stocks of current IC's in this 'chip shortage' - even affecting some more hobbyists uC IC's etc)

I seem to recall recently finding a company that had done EEPROM versions of fast GAL's / 8bit PROM's, that would be OK when these were used in video character to pixels generation. But a neat solution for replacing 4bit ones, some distance apart isn't too easy.

Last edited by ortek_service; 2nd Oct 2021 at 6:14 pm.
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Old 2nd Oct 2021, 6:59 pm   #749
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Default Re: MK14 schematic revisions

I think the main complication with using 2114s in place of 2111 is the reduced number of CE pins - 2 on 2111, only one on 2114 as far as I remember, so the two original CE signals would have to be combined into a single CE off-chip. I agree it would feel silly to squander the extra memory in the 2114s, but just think of them as a cheap 2111 substitute. Both of my ZX81s have 16K RAM fitted internally in the form of a 32K SRAM, of which fully half is not used at all. I don't worry about that too much.

If you were going to get to the point of say removing the CPU, plugging in a memory (RAM + ROM) daughterboard in and then plugging the CPU into that then the daughterboard might as well use 8 bit wide RAM and ROM. The main reason for using 2114 vs. 2111 would be to maintain an approximately original appearance while allowing the use of ICs which are much cheaper and more widely available.

For now.
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Old 2nd Oct 2021, 7:15 pm   #750
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Default Re: MK14 schematic revisions

I seem to recall that when I look at the schematic, some of the extra CS inputs weren't doing much, being always high / low or went to an upper address line, that you could use on a 2114 etc to map-in more RAM. So could map in quite a few of the usual extra spaces quite easily

Yes, I had considered using a 32K SRAM inside ZX81's, as rather more common / cheaper than 16K ones. I presume there's incomplete original ROM etc. address decoding, that stops you using the full 32K, as there should be 56K left in the map. But might be able to get the full amount with some extra logic addition.

Luckily, I think I've probably got a life-time supply of 2114's etc, after getting these v.cheap (and all seem to work) from various radio rallies over the years. Although I have been using quite a few (fortunately all worked OK), to restore an original Acorn System RAM board, that had been raided of all IC's. Although 2114's are still fairly cheap compared to earlier lower-capacity ones.
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Old 2nd Oct 2021, 7:49 pm   #751
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Default Re: MK14 schematic revisions

Good that you got your oldish PC working online again.

With regard to the unused 16K on the ZX81s, it's really just the fact that BASIC does not look for it so while you can map the additional memory into the empty area by adding a few gates, the only reason to do it would be to hold machine code etc, it wouldn't give you extended memory for BASIC. Even back in the day, there were RAM packs which granted the machine well in excess of 16K memory. I dare say a small mod to the original ROM code might encourage it to look for and use RAM above the original upper limit for BASIC.

Although I do have original 16K RAM packs for the ZX81s I always hated the way they (a) spoilt the graceful lines of the base machine and (b) made it exponentially less reliable and more motion sensitive. I get great pleasure from seeing something like 3D Monster Maze running on the basic wedge machine without an ugly looking wobbly block hanging off the back. Unfortunately I still get killed a lot but now mainly due to my own ineptitude, and not because the RAM pack wobbled.

Since you have the ability to program BPROMs one possibility is to use one as a custom MK14 address decoder in the same fashion in which they were used in at least one of the NASCOMs, that would let you do most? All? Of the address decoding with one chip. The best reason not to do that is the amount of current those BPROM ICs draw so if you have the wherewithal to design and program a GAL, better to use one of those.
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Old 2nd Oct 2021, 8:14 pm   #752
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Default Re: MK14 schematic revisions

Quote:
Originally Posted by ortek_service View Post
I seem to recall that when I look at the schematic, some of the extra CS inputs weren't doing much, being always high / low or went to an upper address line, that you could use on a 2114 etc to map-in more RAM. So could map in quite a few of the usual extra spaces quite easily.
From Slothie’s schematic, one of the chip selects is from A10 on one pair and /A10 on the other, so would be quite easy to replace the four 2111s with only two 2114s. With a wire link to the remaining address line you could then make half of the shadow ram areas unique.
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Old 2nd Oct 2021, 10:45 pm   #753
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Default Re: MK14 schematic revisions

When designing the Rev 1.2 board the question of using 2114s as a option came up and the only reason I didn't make it compatible with 2114s (since the pinout is similar with the address and data lines) was that the position of the GND pin moves and along with the chip select signals it would have been hard to arrange for the board to support both 2111 and 2114 chips. I wanted to use 2111 partly because of authenticity but mainly because I had acquired quite a few AMD 9111 and 62X61chips!
But as Mark points out, you can make an adapter board that will replace all the RAM chips with a pair of 2114 RAMS fairly straightforwardly.

When I built my replica I used turned pin sockets for the RAM, and PROM as they take turned pin headers and make building adaptors easy without damaging DIP sockets, because I didn't expect to be able to RAMS or get PROMs programmed in time.

I have actually made an adaptor to allow the use of a 2716/2816 EPROM instead of the PROMs but didn't need to use it, although it might be useful if I ever want to customise the OS for some reason.
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Old 4th Oct 2021, 8:22 am   #754
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Default Re: MK14 schematic revisions

I've been catching up with these latest posts mentioning 2114s and programming TESLAs.
Exactly 2 years ago I posted a 'Simple Programmer for TESLA' {q.v.} and demonstrated that the Czech programming
protocol is identical (?) to that for the earliest Texas Instruments PROMS. The TI data was attached.
The peripheral circuit is a basic 'what if SoC had MH74S- chips?' based on their DM74S- circuit. Which was also used by Acorn.
Whatever whizzo processor is chosen (I used my MK14) it will have to produce the same, sluggish, pulse sequences to suit the PROM.
There was a later thread 'A More Useful MK14', describing 2114s onto an Issue 5, which might be of interest.
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Old 4th Oct 2021, 11:06 am   #755
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Because the available information regarding programming of the Tesla devices was so poor and not in a convenient language (for us), anyone who has come up with a working unit since then will no doubt have perused all available information on the subject including your project thread - this site is never far from the top of the list of google hits for a search on any subject which lies within its remit.

As far as I remember you were kind enough to post the code for the Tesla-modified version of the PROM editor, it would be good if, for completeness, you could also add the Tesla-modified version of the block programming program, if you ever completed that, to the thread (you would have to ask for the thread to be re-opened but the mods are generally very helpful in that respect).

As I mentioned at the time, the only drawback with the project being MK14 based was that in many cases people would be seeking to program PROMs as the last step towards getting an original machine or replica working, so for those cases there really needed to be a 'spin' of your project which was not based on the MK14 itself. As you can see from Owen's notes above, this is starting to happen. I can understand Owen and Chris choosing to use the timing / algorithm of a commercially made Elnec programmer as their main benchmark because that would have been one of the few commercial programmers made with the approval of the chip manufacturer and based on exact information supplied by them.

I think Slothie's project (should he ever get the chance to bring it to completion) will be based on the ubiquitous Arduino so it will be one which is available 'to the masses' rather than limited to people with retro hardware.
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Old 4th Oct 2021, 4:51 pm   #756
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Default Re: MK14 schematic revisions

Quote:
Originally Posted by Mark1960 View Post
Quote:
Originally Posted by DeltaAlpha52 View Post
My current setup uses a bigger display but on a veroboard and is a bit messy
What display type did you use? Do you have a schematic or sketch of connections?
Hi

The ones I used on the vero board were "Oasistek TOT-3301AH-N 7 Segment LED Display Red 3 Digits/Dots 8.8.8. MBD004" from ebay - maybe still available, but are "old" stock . Using 3 of these gives 9 digits. They are (0.30”) 8.0mm digit height • Common Cathode.

The layout was defined in text on the ebay listing

”Hard to explain on eBay with just txt but see if you understand :

g. f. Gap. p. a. b. top pins

8. 8. 8. DISPLAY

1. 2. 3. e. d. c. Bottom pins
Cathodes”

and there seem to work well on my MK14.

Have got some of the .28 display ones and hope to set them up using the Trevor's PCB.

David
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Old 4th Oct 2021, 7:05 pm   #757
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I think Slothie's project (should he ever get the chance to bring it to completion) will be based on the ubiquitous Arduino so it will be one which is available 'to the masses' rather than limited to people with retro hardware.
I have a hardware design and PCB finished, I'm just waiting on completing simulations of some of the analogue bits of which I am least sure to give me the necessary level of confidence to get some PCBs made. I still need to write all the software for the Arduino too, although I do have some I wrote a couple of years ago that might work I've given it a look over and there are many ways in which it could be improved, and a few bits that need changing to reflect some changes in the hardware.

Things have been on hold somewhat since activity restarted on the Ortonview.
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Old 4th Oct 2021, 7:22 pm   #758
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I know, I don't really want to bounce you off that track as you seem quite interested in making progress there.

Truth be told we are quite well served, one way or another, for the ability to make MK14 PROMs at the moment and everyone in our immediate group who needed programmed PROMs at one point or another now has them as far as I know, so the Tesla problem can probably wait a little bit longer.

It's been a long haul since I originally naively said 'I can programme those!' only to find myself holding a pair of TESLA MH74S571s which I had not even realised existed up until that point. That original pair of PROMs ended up going off on a grand tour of Europe, I recall.
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Old 4th Oct 2021, 7:35 pm   #759
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Quote:
Originally Posted by SiriusHardware View Post
It's been a long haul since I originally naively said 'I can programme those!' only to find myself holding a pair of TESLA MH74S571s which I had not even realised existed up until that point. That original pair of PROMs ended up going off on a grand tour of Europe, I recall.
Yes, those PROMs started life in the Czech republic, ended up in Poland where I bought them, sent them up to you and from there to France and Germany before returning to me. Those PROMs have travelled to more places than I have.
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Old 4th Oct 2021, 8:27 pm   #760
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Default Re: MK14 schematic revisions

I have a bag of them as well awaiting an effort for me to build something - gonna wait for the Slothie machine I think...
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