Yet another MK14 vdu card

[Mark1960]

I have definitely seen IDC female sockets but not recently, and don’t remember seeing IDC male plugs.

[SiriusHardware]

IDC male and female PCB mount and IDC female cable mount are still current and widely available, but the DIN card rack connectors are maybe less so nowadays. Have you ever seen a DIN 4xxxx data connector designed to clamp onto a flat ribbon cable? I don't think I have.

[Slothie]

Rapid has a cable mounting 41612 connector (Order Code: 51-9676) , so presumably others with a wider range of stock would too. Although where you get the 64 way ribbon cable from is a good question....

[SiriusHardware]

For Coolsnaz2's proposed one-to-two splitter cable one of the three cable mounted connectors would have to be male, the other two female. Are they available in both 'sexes'? (At work, don't have time to look).

[Slothie]

Originally Posted by SiriusHardware

For Coolsnaz2's proposed one-to-two splitter cable one of the three cable mounted connectors would have to be male, the other two female. Are they available in both 'sexes'? (At work, don't have time to look).

Sadly it looks like they only have the female type. Farnell has a range most of which are marked "no longer manufactured" which is not a good sign either, unless you've got that time machine working....

[Slothie]

Digikey has male and female a+c style connectors, at about £12 each....

[SiriusHardware]

I think Tim and Cs2 both use the more closely spaced a+b row type but it seems possible Digikey etc may have them in their range, again, don't really have time to look.

[coolsnaz2]

Just remembered, Coolsnaz2 has an original VDU and issue V MK14 and I'm sure he also added a RAM / ROM expansion into the 0200-07FF memory hole as well? - so he may well be the first to be able to run Invaders on an original MK14 and original VDU.

I created a memory board which plugs into my existing backplane, with another connector on the front for the VDU card, see attached photo.

Attached photos shows Realtime's Invaders program running on my original MK14 and original VDU card. Sorry about the top line being missing, this is due to the old TV being used.

[SiriusHardware]

It amazes me how often we mention something off-hand, and you quietly go away and several days later, it's done. So that's great to see, Invaders running on nearly all original SOC hardware (there never was an official 'RAM pack' for the 0200-07FF slot from SOC, so homebrew was always the only way to go).

I don't recognise the TV (though there will be plenty of people on the forum who do). Do you know what make / model it is? Edit: I see Alba, but I still don't know the model.

It probably has a 'V-Height' control around the back somewhere, it may even be poking out through the back of the set. They also sometimes have horizontal width and / or horizontal shift controls which might let you centre the image a bit more - however the latter issue is the purely fault of the SOC VDU design, which has always generated its image offset to the left.

[coolsnaz2]

SiriusHardware

TV is a ALBA CTV 14RS, unfortunately no V-Height adjustment on the outside of the case.

[SiriusHardware]

Not even available through a twiddle hole?

I tried looking for a service manual but it is a surprisingly obscure model, which was probably also badged by other low end badgers like Goodmans, etc. If we knew the chassis common to them all we would probably have more luck finding a service manual for that.

Anyway, point proven, Invaders works great on original SOC hardware.

[Realtime]

Originally Posted by coolsnaz2

Invaders program running on my original MK14 and original VDU card. Sorry about the top line being missing, this is due to the old TV being used.

Well, you can’t get much more authentic than that. Superb!

It would be easy to modify Invaders to use 1 or 2 less character rows so that it displays properly with the SoC design VDU cards. I’ll add that to the mods list.

So it’s now been demonstrated on original SoC, Pi based, Ortonview and my VDU card That just leaves the replica SoC Module unless there are any others out there.

[SiriusHardware]

The Czech replica of the SOC VDU is, like the Czech replica of the issue V MK14, virtually identical to the real thing. We don't know the whole story but we suspect that both PCBs were scanned from original SOC PCBs. The only identifiable difference between the Czech replica issue V and the real issue V is that the dome switch contact pads on the replica were laid out for four-point dome contacts where the original issue V used three-point contacts, this being a pragmatic adjustment because the person who made them found it easier to source four-point dome contacts.

So Tim's Czech replica of the SOC VDU is to all intents and purposes a real SOC PCB with the same track layout and circuit. The one thing which might make a difference is the character generator, as I think a slightly different version of the original character generator was supplied with those Czech kits. Even so, I don't think I have ever noticed anything different about the output produced by Tim's replica SOC VDU.

So far Invaders has been tested with:

Your (Realtime's) CPLD based SOC VDU emulator.
Karen Orton's 'Ortonview' (built on a PCB designed by Sothie).
Coolsnaz2's Pi + Dual port RAM based SOC VDU emulator.
Coolsnaz2's original issue V MK14 + original SOC VDU + Homebrew RAM

P.S - no need to modify Invaders because of the height problem, Coolsnaz2's TV is overscanning by a considerable margin. Look again at the shot from my CRT screen in post #63 - no problem with the height there, you can see a faint reflection of the top line of text on the bezel running around the top of the screen.

[SiriusHardware]

One more to add to the diverse range of configurations with which invaders has been tested:-

'Slothie'  MK14 'issue VI' (@4.00MHz) + Homebrew 0200-07FF RAM + Real SOC VDU.

Runs without any problems.

Apologies for the characters being slightly blown out on the image, I had the brightness a little on the high side. Note the image does fit on my CRT screen but I always have the height / width adjusted so that there is not much more than 1cm overscan all round. (screen is 14"). Also notice the image is offset to the left - that is normal for the SOC VDU, and illustrates one way in which both Ortonview and Realtime's CPLD VDU improve over the original.

Do you have an official name for yours by the way, Realtime? 'Realview' springs to mind, but maybe you have already decided on something else.

[Timbucus]

When I get five perhaps after Cambridge I will mod the code / or my wiring on my replica SOC card - it is identical as I also have the same few dots on the left and the missing top row on most TV's as CoolSnaz gets - My CRT's don't have vertical position either...

You are correct it was a compatible char gen supplied but, I have since provided a replacement original chip.

[SiriusHardware]

Hmm, why, was there something awry about the supplied chip?

[Timbucus]

No he had just found stock of DM86S64CAB which looked identical - here are the pictures I posted in the thread to show the two side by side. Original on the right. [EDIT: as in original chip not the S64CAB supplied with PCB]



It was purely me trying to be totally accurate - then I went and patched in the per character inverse board that uses one of the unused bits...

[Realtime]

Originally Posted by SiriusHardware

Do you have an official name for yours by the way, Realtime? 'Realview' springs to mind, but maybe you have already decided on something else.

It hadn't occurred to me to name it, but I think Realview is a great suggestion. I'd be more than happy with that.

[SiriusHardware]

It was just to save us from having to write out 'Realtime's CPLD based MK14 VDU emulator' every time we refer to it, but actually, I have just Googled the term 'Realview' and it already generates a few hits. Maybe you would like to pick your own name for it which is unique as far as the internet is concerned, so if anyone goes searching for it with a view to buying one from you, they don't get led off down loads of dead ends.

[Realtime]

I was listing some of the features of 'Realview' for ScottishColin and thought it would be good to do that here, now that the design is finalised.

• Small form factor - 100x50x20mm (108x50x30 when the DM8678 emulator is fitted)
• It generates proper TV sync (with seration pulses) so works with modern digital TVs and older analogue TVs (no slanted lines at the top)
• Composite video output (no RF output)
• It has onboard Page 0 expansion RAM from 0x200 to 0x7FF so you don't need a separate memory board to get the full 1.5K bytes. That said, the on-board RAM can be disabled by a DIP switch if you already have a memory module fitted.
• It provides an additional block of Page 1 SRAM from 0x1200 - 0x17FF for programs and data (not accessible by the video display).
• Like the original SoC module, it doesn't come with the character generator chip (DM8678CAB) so either you need to source one of those or plug in my emulator module. Of course the graphics mode works with or without the character generator fitted
• The VDU module can be controlled by on-board DIP switches or by the INS8154 I/O chip on the MK14

The photo shows 'Realview' fitted with the DM8678 emulator (and there's a tape interface module in the foreground that also has the expansion RAM fitted).