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Old 11th Oct 2020, 12:02 am   #341
SiriusHardware
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Default Re: Mk14 vdu

A good shortcut, although the original idea was to be able to take any existing ASCII text (the majority of which will be lower case) and transform it into MK14 viewable format.

If you were 'composing' text with the sole intention of displaying it on an MK14 then obviously you would stick to upper case only and not use any characters with codes above 0x7a.
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Old 11th Oct 2020, 11:01 am   #342
Karen O
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Default Re: Mk14 vdu

I think I should look to the original hardware design for guidance on how to drive NENIN, in which event a diode from PIC pin 7 to NENIN (pointy end towards NENIN), plus a pull-down resistor as per original design should suffice.

I think the diode can an ordinary silicon type: it needs to lift NENIN to a minimum of 2.4V, yet the drive from the PIC is approximately 50R to +5V.
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Old 11th Oct 2020, 11:27 am   #343
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Default Re: Mk14 vdu

Quote:
Originally Posted by Karen O View Post
I think I should look to the original hardware design for guidance on how to drive NENIN, in which event a diode from PIC pin 7 to NENIN (pointy end towards NENIN), plus a pull-down resistor as per original design should suffice.

I think the diode can an ordinary silicon type: it needs to lift NENIN to a minimum of 2.4V, yet the drive from the PIC is approximately 50R to +5V.
Oh absolutely. If thats how SOC does it then thats the way it should be done. TBH I was too lazy/distracted to look at the circuit diagram because its on my other laptop and it takes actual minutes to boot it up!!
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Old 11th Oct 2020, 4:56 pm   #344
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Default Re: Mk14 vdu

Success!
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Old 11th Oct 2020, 5:05 pm   #345
Karen O
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Default Re: Mk14 vdu

Find attached zipped key files.


I don't warrant that this version is completely bug free, but any remaining problems are likely to be easy to fix quickly.
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Old 11th Oct 2020, 6:30 pm   #346
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Default Re: Mk14 vdu

Wow - I haven't even started wiring mine yet... Sirius is going to win this one I think. Pictures look great Karen impressive work (again).
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Old 11th Oct 2020, 7:41 pm   #347
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Default Re: Mk14 vdu

Well colour me impressed!
The picture quality is good, none of the often seen "jailbars" etc.

Also, complements on the cute TV! I have a 6" Russian Vega portable, small but nowhere near as cute
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Old 11th Oct 2020, 7:46 pm   #348
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Amazing Karen, an inspiration!
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Old 11th Oct 2020, 8:00 pm   #349
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Default Re: Mk14 vdu

Yes, first impression is that the picture is a lot cleaner especially in graphics mode than on the real VDU.

I'd better get buzzing!
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Old 11th Oct 2020, 9:22 pm   #350
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Default Re: Mk14 vdu

Chip programmed, connections 98% buzzed out. Just have to rearrange the PS4 page select from RE3 to what Karen said.
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Old 11th Oct 2020, 10:14 pm   #351
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Going to have to leave it for tonight, need to purloin a couple of parts from work. Annoying.
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Old 12th Oct 2020, 4:52 pm   #352
Karen O
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Default Re: Mk14 vdu

I've found a bug already - inverse video in graphics mode has a partial right border. Fixed!

I'd be grateful if someone could check over the supplied circuit diagram.
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Old 12th Oct 2020, 6:20 pm   #353
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Default Re: Mk14 vdu

Thanks for the firmware update.

I have now gathered the few remaining bits needed and mine is already wired exactly as per your diagram. As always I'm amazed by how incredibly minimal the hardware is. Sinclair would have loved it.

I should be ready to crank mine up a little bit later on tonight. Will report back with whatever happens.
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Old 12th Oct 2020, 7:32 pm   #354
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Default Re: Mk14 vdu

OK:

On powering up, the correct 0000 00 prompt is shown on the MK14 but, depending on the address being displayed, only one or two of the address digits is at normal brightness, the rest being very dim. The 7-segment display refresh rate looks quite slow. As I step through the addresses with MEM, other digits go bright and the original ones go dim, or the 'segment brightness' cycles across the screen in a manner reminiscent of 'Duck Shoot'.

Despite the disturbance to the display scanning rate, I can look through any area of the RAM and I can edit any area of the RAM -except- the 512-byte block from which the VDU is rendering.

At the moment the VDU is pointed at the extra-extra RAM 0200-03FF and if I look through that area with the monitor it all reads out as 'FF' - which is not normal, as it normally initialises to random values. If I try to change those values using the monitor, I can't. Going back to them, they still read out as 0xFF.

The VDU shows a rock steady screen full of '?' which reflects the apparent content of the memory (the top bit is ignored, so FF will give '?', the VDU code for which is 0x3F).

If I change to graphics mode I get a pure white block on the screen, again reflecting the apparent value of 0xFF being read from all locations in the screen RAM.

Normal service is resumed if I unplug the PIC-VDU and plug the SOC VDU back in.

I'm going to park it there for now, and we'll let Tim build his version and see what his does. His system is 'cleaner', as he doesn't have the extra-extra RAM on his.

I should say that this is using the V1.01 firmware from Karen's post #352.
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Old 12th Oct 2020, 7:52 pm   #355
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Default Re: Mk14 vdu

Good results so far then at least the MK14 VI continues to work when it is plugged in - I am gathering bits at the moment and will try and get a build underway one evening this week.
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Old 12th Oct 2020, 7:54 pm   #356
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Default Re: Mk14 vdu

A little bit more info:

If I have the PIC-VDU connected but disable it (VDU_ON=1) then the MK14 functions completely normally and I can edit any RAM including the RAM which the VDU is set to render from, and the edited values 'stick'. So for example if I have the VDU pointed at 0200-03FF and I turn the VDU off, I can use the monitor to change values in that address range and they stick.

If I then re-enable the VDU and look through the locations 0200-03FF they then all read as 0xFF even if I previously successfully changed their content with the VDU disabled.

If I then disable the VDU and look through the address range 0200-03FF, the values in the screen memory block STILL read back as 0xFF.

If I use the monitor to edit them again, the edits are accepted.
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Old 12th Oct 2020, 7:56 pm   #357
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Default Re: Mk14 vdu

When you re-enable it does it show what is in memory or still #FF?
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Old 12th Oct 2020, 8:09 pm   #358
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Default Re: Mk14 vdu

Quote:
Originally Posted by SiriusHardware View Post
A little bit more info:

If I have the PIC-VDU connected but disable it (VDU_ON=1) then the MK14 functions completely normally and I can edit any RAM including the RAM which the VDU is set to render from, and the edited values 'stick'. So for example if I have the VDU pointed at 0200-03FF and I turn the VDU off, I can use the monitor to change values in that address range and they stick.

If I then re-enable the VDU and look through the locations 0200-03FF they then all read as 0xFF even if I previously successfully changed their content with the VDU disabled.

If I then disable the VDU and look through the address range 0200-03FF, the values in the screen memory block STILL read back as 0xFF.

If I use the monitor to edit them again, the edits are accepted.
Is there a pull up on NWDS? From your description it sounds like the VDU is writing FF to every location it accesses.
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Old 12th Oct 2020, 8:17 pm   #359
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Default Re: Mk14 vdu

Quote:
When you re-enable it does it show what is in memory or still #FF?
You mean what does the VDU show when I edit the screen memory with the monitor while the VDU is disabled, verify that the changes have actually been made, then re-enable the VDU?

It shows a screen full of question marks (consistent with all locations containing 0xFF). At this point, if I look through the screen memory block with the VDU enabled I see all 0xFFs.

If I then disable the VDU and look through the screen RAM again, it still contains 0xFF all the way through.

I know you're going to ask, so, no, I don't have the NRDS output from the PIC-VDU connected to NWDS on the MK14 instead of NRDS. I did check though.

Last edited by SiriusHardware; 12th Oct 2020 at 8:26 pm.
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Old 12th Oct 2020, 8:20 pm   #360
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Default Re: Mk14 vdu

Quote:
Originally Posted by Mark1960 View Post
Is there a pull up on NWDS? From your description it sounds like the VDU is writing FF to every location it accesses.

Yes I'm thinking there should be a pull-up on NWDS and NADS. Fortunately something easy to test.
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