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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 15th Apr 2019, 11:53 pm   #61
Timbucus
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Default Re: MK14 programming interface - MK2

Hmmm - it is the same brand SGS 74LS365BI also marked 9844I
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Old 16th Apr 2019, 12:09 am   #62
SiriusHardware
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Default Re: MK14 programming interface - MK2

To be exact, this one is marked SGS 74LS365ABI 98441 - I think you probably just missed out the 'A' after the '5' on the one you have there.

Anyway, you'll be able to try it for yourself, I will get it on the way back to you ASAP.
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Old 16th Apr 2019, 12:15 am   #63
Timbucus
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Default Re: MK14 programming interface - MK2

No actually there is no A so maybe a look at the data sheet is needed or these are re topped devices with a printing error... I have 5 more in transit towards the VDU project
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Old 16th Apr 2019, 12:27 am   #64
SiriusHardware
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Default Re: MK14 programming interface - MK2

It does seem slightly suspicious that two devices would have different main device suffixes and the same batch number.

Your mention of 365s being used on the VDU made me leap across to look at mine to see if it had alternative 365s in it that I could try in the MK14 - but of course the devices in the IC9 / IC10 positions in my VDU are... 80L95s.
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Old 16th Apr 2019, 1:06 am   #65
Timbucus
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Default Re: MK14 programming interface - MK2

Well tried finding the relevant datasheets but, no joy - the general SGS sheets on 74LS series say the suffix should be B for a DIP - I wonder if it is a different manufacturer - maybe a CMOS part or an original 74365 non schotty even. TI parts had an A after them. I am going with a relabelled chip of unknown exact design due to your observation on the BATCH number...
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Old 21st Apr 2019, 7:50 pm   #66
Timbucus
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Default Re: MK14 programming interface - MK2

As a quick update - putting the SGS 365ABI back in my machine allows the PI-Programmer to run at full speed fine although still with the longer reset... go figure. I also tried one of the four TI marked 365AN I have bought for the VDU circuit and that works fine as well. There must be some other issue though as it affected SH so badly. The review of the kit in PCW issue 2 (Apr 1978) lists different values for some passive components - perhaps we also need to look at those - I went with the list in the manual maybe SH Issue II has these older values?

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Old Yesterday, 10:24 pm   #67
SiriusHardware
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Default Re: MK14 programming interface - MK2

Just catching up as I have been off grid for the whole of the Easter weekend. Those new results with the original 365 are just bizarre. I've just arrived back but I will take a look at the components on mine, especially in the reset area since they seem so different in that particular area. Why can mine be reset so much faster?

Can you just confirm that your reset opto collector resistor really is 120R, not some other value? If it were bigger then obviously it would take a lot longer to discharge the reset capacitor.

I've also just checked that mine really is 120R - since I used SM resistors throughout for mine, it would have been all too easy to make the mistake of putting a part marked '120' (12 ohms) in there instead of '121' (120 ohms).

I've also managed to wangle a quantity of TI SN74LS365 sourced directly from RS UK, you are welcome to a handful of those (free) if you want them - the least I can do after all the beta testing you've been doing.
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Old Yesterday, 10:46 pm   #68
Timbucus
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Default Re: MK14 programming interface - MK2

Yes just checked reads 119.5 ohms with a meter

Sounds like a good offer - interesting if you get the same result with one of them in which case we need to look further afield - maybe send the chip back to you as well as it has an effect for you if they don’t.

On a lighter note I have patched the programmer into an interface on my conversion of Daver’s fpga MK14 onto my Waveshare Spartan board this weekend!

It downloads and plays segtris fine but moonland failed (as does daver’s Built in copy so probably a vhdl bug) - message also transferred fine as well - no reset on that interface though so does not add to this problem solution...
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Old Yesterday, 11:49 pm   #69
SiriusHardware
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Default Re: MK14 programming interface - MK2

I think Daver... (for the benefit of others here on this forum we are referring to a user on the Vintage Computer Forums who has made a virtual MK14 - still a work in progress - in VHDL) ... Daver would be very interested to hear your feedback on that, or might be even more interested if you fixed it first and then told him.

There is one potential problem that I can think of, and that is the way an offset of -128 is treated by some instructions and not others. For pointer instructions an offset of -128 means 'Use the current contents of the E (Extension) register as the offset', whereas with some others - jump instructions? -128 is just an offset like any other possible value.

I can't remember the specifics but I think in the case of some emulations there is an assumption that an offset value of -128 always means 'use the value in the E register as the offset for this instruction', in which case any code which happens to include a jump instruction with a -128 offset will fail.

I might not be remembering this correctly - Karen is going to be the expert on this one.

Last edited by SiriusHardware; Yesterday at 11:56 pm.
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