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Old 10th Apr 2019, 5:08 pm   #41
Timbucus
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Default Re: MK14 programming interface - MK2

Ah yes silly me 500Hz 1ms High and 1ms Low - looks like I need a frequency meter...
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Old 10th Apr 2019, 5:45 pm   #42
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Default Re: MK14 programming interface - MK2

I don't see why, you measured it perfectly well with the scope. In fact, I picked that frequency so it would be intuitively easy to read on a scope (pulses exactly 1 square wide at 1ms/div).

A lot of medium to high end DMMs can measure frequency up to a couple of Mhz or so, so it might be worth having a closer look at what you have.

Anyway... that rules out an overall speed problem, your MK14 certainly isn't stuck in third gear.
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Old 11th Apr 2019, 3:09 pm   #43
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Default Re: MK14 programming interface - MK2

Well had a chance to test again with a scope on the Reset line and it seems I need to set the time.sleep hold low to 0.1 and recover to 0.2 to match the actual shown on the scope with the onboard reset which varied from 0.1 to 0.4 low, but was always a 0.2 recovery. With the figures I was using (and the default) there was no visible hold low on the scope.

Good news is I tried the other original style display (I bought another Texet on which the keyboard is dodgy) and I was able to set the key press values back to default. It seems to go in pretty quick and reliably now with the reset extended. I put my original display back in and it still works so maybe it was the reset settle time all along. The 365 is already on the way to SH but, I think that is probably a red herring. You never know maybe the specific chip has issues - I had already sent it before I discovered the reset timing.

Here is the manual, default and final view of the reset sequence...

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Old 11th Apr 2019, 5:11 pm   #44
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Default Re: MK14 programming interface - MK2

That looks really promising, and I'm glad you are finally able to see the uploader operating in its full on 'Turbo' mode. It must have been quite disappointing to have to run it in slow-mo as you did earlier.

I'm really grateful for your efforts to provide all of this detailed feedback because without one of those variants to play around with, there would be very little I could have said to people beyond 'try playing with all the time constants'. Nor would I have known (or guessed) about the different keypad edge connector pinout if you had not pointed that out.

As a matter of interest what is the marked value of the reset capacitor in your JM machine? I'll take a look at the value of the capacitor in my original machine when I get home. It may very well be that the value of that capacitor changed from one original MK14 issue to the next, it may even have depended on whatever S.O.C. could lay their hands on for the right price at the time. In most cases the value of that capacitor would not be critical at all.
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Old 11th Apr 2019, 7:45 pm   #45
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Default Re: MK14 programming interface - MK2

Quote:
Originally Posted by SiriusHardware View Post
That looks really promising, and I'm glad you are finally able to see the uploader operating in its full on 'Turbo' mode. It must have been quite disappointing to have to run it in slow-mo as you did earlier.
Indeed it is much better especially with the longer programs like ONEARM and SEGTRIS

Quote:
Originally Posted by SiriusHardware View Post
I'm really grateful for your efforts to provide all of this detailed feedback because without one of those variants to play around with, there would be very little I could have said to people beyond 'try playing with all the time constants'. Nor would I have known (or guessed) about the different keypad edge connector pinout if you had not pointed that out.
Actually I am pretty certain this is the fun part and I have really enjoyed doing some electronics again - once they are running computers are a little less interesting!

Quote:
Originally Posted by SiriusHardware View Post
As a matter of interest what is the marked value of the reset capacitor in your JM machine? I'll take a look at the value of the capacitor in my original machine when I get home. It may very well be that the value of that capacitor changed from one original MK14 issue to the next, it may even have depended on whatever S.O.C. could lay their hands on for the right price at the time. In most cases the value of that capacitor would not be critical at all.
Mine is a 22uF 25v but, its one I had left over from a set for recapping a Spectrum, not a well known brand so could be a bit variable. I seem to need to do about two or three resets from Cold power on before it works so there may be something lurking around that CAP.
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Old 11th Apr 2019, 9:15 pm   #46
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Default Re: MK14 programming interface - MK2

I've just tried to look, but, typically, the value and voltage are on the PCB facing side of the capacitor body so I can't see them. However I have just found my original very frail board layout / component list, and C6 is given as 22uF 16V.

It may (ironically) be that my 40+ year old capacitor actually has very little capacitance left (could be almost dried up) so it might be acting more like a 1uF, which could explain why my system tolerates a very short reset hold and release time.

The reset capacitor is the only electrolytic on my MK14 - I have nothing fitted in the C2 position because the power transformer, rectifier, smoothing capacitor and regulator are all mounted offboard, the latter on a 5cm by 6cm multi-finned heatsink, and it still gets quite warm.

Did you get around to trying an alternative (non switch-mode) supply to see if that makes any difference to your occasional manual-reset difficulties?
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Old 12th Apr 2019, 11:02 am   #47
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Default Re: MK14 programming interface - MK2

High peeps! Sorry I've been silent for a while but I've been having health problems and in fact tomorrow I have eye surgery because vision is deteriorating in my right eye. They expect good results so hopefully I'll be back on form. Working on Electronics and PCBs has been too tiring and frustrating for me, so no progress on the PROM Programmer, uploader etc. I did manage to route all the VDU signals to the bottom of the 32 way connections but I need to check everything before I send off the files for manufacture.
as far as the SMPSU is concerned, when I put the scope on the power connections and signals there was a huge amount of high frequency noise because even on original MK14s there is very little decoupling and Electrolytics dont work well at high frequencies. I'm going to scatter a few extra 0.1uF caps and see if that improves matters.
It's great to see more people being sucked into the MK14 world
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Old 12th Apr 2019, 5:08 pm   #48
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Default Re: MK14 programming interface - MK2

Ouch, just thinking about that makes my eyes water - take care, we need you back in 100% working order as you are still our brightest hope for a VDU - friendly replica board, not to mention a Tesla compatible PROM programmer. So no pressure, then...
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Old 12th Apr 2019, 8:18 pm   #49
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Yes indeed good luck with the operation - I have several TESLA PROM's waiting for your full recovery and maybe a third MK14 kit on such an amazing sounding replica board...
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Old 12th Apr 2019, 10:00 pm   #50
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Default Re: MK14 programming interface - MK2

Lol looks like Sirius has been doing a great marketing job!
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Old 12th Apr 2019, 10:19 pm   #51
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Default Re: MK14 programming interface - MK2

Slothie, SH has been singing your praises - credit for making your own PCB by the way...

Looking at the signal on C3 on my JM there is quite a bit of noise on the 5V measured while using my NorthPada 9V SM PSU - which I use for my Spectrum Next and my DSO small scope.

Hopefully I have remembered how to use the bigger scope to show the pulsed nature... feel free to point out the errors in my settings it has been a while since I did this sort of thing.

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Take any measurement accuracy with a pinch of salt: XIN shows a clock pulse on 0.5uS per div with just under four peaks across two divisions so probably 3.8MHz so a bit low for the 4MHz crystal - it's not really a square wave but a sine wave which I assume is due to the limits of the scope - I was sure it was 20MHz but, maybe I was wrong.

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I will change over the connector polarity tomorrow and try a Spectrum PSU to see if that is gone and has an effect on the reset.
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Old 13th Apr 2019, 12:48 am   #52
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Quote:
Originally Posted by Timbucus View Post
Take any measurement accuracy with a pinch of salt: XIN shows a clock pulse on 0.5uS per div with just under four peaks across two divisions so probably 3.8MHz so a bit low for the 4MHz crystal - it's not really a square wave but a sine wave which I assume is due to the limits of the scope - I was sure it was 20MHz but, maybe I was wrong.
That looks about right for a 4Mhz signal on a 20MHz scope. Don't forget the "20 MHz" is the analogue bandwidth, the point at which the signal level of a sine wave input is attenuated by 3dB or 50%. To make a square wave look square you need a bandwitdth many times the base frequency because it is these higher frequencies that make the corners of the waveform look square.

Your 5v looks really clean compared with what I got with a Switched Mode supply! Mind you I was using a really cheapo Orwon digital scope someone gave me, my best scope (a Phillips/Fluke 4 chan 100 MHz scope is in storage at the moment.)
The SC/MP divides the XIN frequency internally by 4 so activity on the power pin is due to sudden high current usage internally so the pu;ses on the power rail may just be caused by 1Mhz pulses delayed by tiny amounts across parts of the chip, so don't worry if they don't conform to what you expect. Also your scope has input capacitance so applying it to XIN may 'detune' the crystal cscillator - c1 is only 22-33 pF. and many scopes have input capacitance of 50pF. In some cases applying a scope to a quartz crystal can actually stop the oscillation!
You might get a more accurate frequency reading by looking at XOUT - or you might stop the oscillator as mentioned. This shouldnt do any damage though.

Those Hameg scopes are nice scopes BTW, a friend of mine had one and it was really lovely to use for basic scoping around.
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Old 13th Apr 2019, 2:18 am   #53
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Quote:
Originally Posted by Slothie View Post
Lol looks like Sirius has been doing a great marketing job!
There's been no need, your handiwork speaks for itself.

One thing I wanted to ask - how did you lay out the keypad edge connector on your PCB? The way JM ordered the connections is perfectly reasonable and logical given the lack of detail, especially pin numbers, on the original circuit diagram.

Also, I would have been very tempted to untangle the mixed up order in which the 8154 port A and B pins arrive at the rear edge connector but since these connections were well documented in the manual I would imagine that your PCB, the JM boards and the Czech PCBs all follow the original layout.
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Old 13th Apr 2019, 5:55 am   #54
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Default Re: MK14 programming interface - MK2

I followed this circuit diagram I'm pretty sure
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Old 13th Apr 2019, 2:12 pm   #55
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Default Re: MK14 programming interface - MK2

I had a copy of that and another as a BMP but, the diagram is not that clear on the numbers and the other scan was cut off. But, this is what I believe it should be:

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Of course physically the numbers run from 1 by the reset switch to 16 on the bottom. So PAD 6 should be to PIN 10 on IC13 and PAD 8 should be to PIN 11 on IC13 on a real MK14 V5.

The JM board is slightly different of course as described above as it runs 1:1 with PADS 3-12 mapped to PINS 1-11 (missing 8 which is Ground) on IC13 so directly to 0-9 on the BCD decode. It does do the swap of 13 and 14 so 14 will generate ABCD__EF and 13 will generate _,_,GO,MEM,ABORT,_,_,TERM

Slothie - Thanks for the help on the Scope - it was Dad and Mine's prized possession in the 1980's. I did reread the manual and spot the mention of the square wave range and capacitance after I posted. I failed the electronics side of my Radio Ham in 1980 but, passed O Level Electronics 2 years later - probably not done that much since until the last year or so, so all help appreciated.

SH - I can confirm that so far the JM top connection is the same as on the diagrams and boards I have seen, so as you say that is probably not a good idea to change - but, adding the SoC recommended connections for the VDU as the standard for the underneath is good.

The cost of my board just jumped as I had an Invoice for 32 import from FedEx for my chips from UTsource that came last month - and they charged me 12 admin for paying the customs fee for me! So beware all...

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Old 13th Apr 2019, 6:30 pm   #56
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Default Re: MK14 programming interface - MK2

In addition I was just browsing through ETI back issues (sad I know) and found the review of the MK14 version 1 on Page 27 of the August 1978 issue - it's mentioned on the cover as well with the Space Shuttle...

https://www.americanradiohistory.com...1978-09-78.pdf

That is relevant to our thread as it confirms the above with a nice diagram of the edge connector although it calls the columns 1-10 confusingly...

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Old 14th Apr 2019, 9:49 am   #57
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Great find, Tim. As a matter of interest 'Practical Electronics' also often included little snippets and bits of code for the MK14 - have a look through issues of PE for 1978 through to about 1980-81 on the same website.

The only 'sad' thing about reading those is that there is no longer the width and breadth of people interested in hobby electronics to support a 'population' of good magazines like ETI. But that's another whole subject.

I liked the ETI article especially for the helpful information about the keypad connector layout and external keypad matrix as it relates to the actual physical connections - I have never seen that info presented in print anywhere else.

It's amusing that they found the keypad so bad that they felt the need to include the remedy in the review. Unfortunately that certainly did mirror the experience of all of us with those early-issue machines. It's also interesting that the revised monitor was already being discussed / planned at that very early stage. I had not used the 'old' monitor for 40 years until recently, when I programmed an EPROM with it and grafted it into the MK14 to test the uploader's compatibility with it when set to work with that version. It was seriously clunky, much more laborious to use than I had remembered.

Another point of interest in that ETI issue comes not from the review itself but from the early version of the MK14 advert just a few pages into the issue. The illustrations of the machine and the manual were obviously both drawn by someone who had never seen either in their final form, unless the issue I really did look like that, with around half of the ICs vertically oriented. The manual is drawn with a flat spine, which was never the case as far as I know. Later versions of the same advert represented the machine much more accurately and were actually quite attractive, with the drawings of the MK14 (and in a later version, its peripherals) drawn in a fine 'woodcut' or 'engraving' style.

This also reinforces what I've found elsewhere - that the MK14 seems to have appeared in 1978, contradicting what I had believed for years, that it was launched a year earlier. In my old video for the original microprocessor based version of the uploader, one of the captions reads 'A 1977 vintage MK14 microcomputer'. Unfortunately it's a bit late to change that now.
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Old 14th Apr 2019, 10:26 am   #58
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Indeed I found that advert and thought it very early. The first mention in ETI is in the March 1978 issue in Microphile - they make it sound very mysterious:

"THE FIRST ITEM WE look at is from a company thought by some to like the cloak and dagger game, but then so do quite a few semiconductor manufacturers, Science Of Cambridge - don't mention Sinclaur (sic). At the time of going to press they have just launched their MK14 with an advertisement in a magazine that is generally not associated with a dedicated commitment to micros."


Their advert does not actually appear in that issue of ETI but, an even earlier one with a funny looking MK14 does appear in the April issue - take a look. I suspect this was the classic Sinclair "it's working on a breadboard" so get the adverts out before it was even finished - that pictured device certainly does not have the IO chip!

Not sure which magazine they mean (I remember someone mentioning Practical Wireless perhaps?) which if ETI had seen it (or had mates on the advert desk who rang them, not unreasonable if it was mainly electronics that they pass on snippets of news to a more digital focus magazine) would have had to be the Feb/Mar issue which would have appeared in Jan/Feb so Sinclair would have booked and supplied the artwork very early January.

The other find was the other article of the above mentioned series on adapting the EX42 keyboard which is in the Sept 1984 issue on Page 22. As an aside but, sort of ties in with tape controls we were talking about, there was in the same issue, an article on digital control of a tape deck - this does not mention, but reminds me of an article by Williamson somewhere which I cannot find where he suggests developing such a system.

Finally Jan 1978 Page 74 has a great little idea (which could be added to the MK14 Cassette Interface) to defeat the AGC on tape decks by superimposing a continuous HF signal...

Between Dad and I we used to get ETi, Hobby Electronics, Practical Electronics almost every month and Elektor quite often. There are now some magazines emerging to support the 'maker' market around the PI and the Arduino which is heartening as creativity is not a common skill these days. I also think that the demise is very much due to online availability as well replacing paper but, it just doesn't feel the same.
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Old 14th Apr 2019, 10:50 am   #59
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Default Re: MK14 programming interface - MK2

Re-reading that earlier advert it mentions only 14 chips not the 18/19 in the V1 - so I think the IO (and from the picture the external keyboard connector) may have been a late addition...

ETIFirstAdvertApril1978.pdf

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Old 15th Apr 2019, 11:47 pm   #60
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I took the MK14 to work and removed and examined the original reset capacitor - to my surprise it looked healthy both on the component analyser on my Hameg scope - yes, I have one as well - and on a capacitance meter which showed the value to be 24uF. I replaced it anyway with a new capacitor, value measured at 24uF.

On getting it back home, I tried it and it worked exactly as before, not too surprising when the original capacitor turned out to have been reasonably OK.

I then tried Tim's 74LS365 in place of my original 80L95 and... although the MK14 started up normally and responded to keypresses in the normal manual sense, fitting that chip in my MK14 broke the uploader.

It doesn't even work for me if I lengthen the reset hold and reset release times (only) to Tim's new values - I see the MK14 reset much more slowly and deliberately but it then completely ignores all the input keypresses which follow, as they are obviously not being applied for long enough to be detected when the 365 is fitted. I suspect I would have to increase those timing values (as Tim originally did) in order to get it to work.

I didn't go any further, since this seems proof enough that there is some sort of difference between Tim's 74LS365 and my 80L95. I'll send the chip back in the next few days.

Tim, what brand is the 365 you currently have fitted in your JM MK14? The one I have here from you is an SGS branded device (SGS-Thompson, I presume). Is the one you have fitted now the same brand, or different?
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