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Author Topic: Printing 'block' of text  (Read 3954 times)
retroshaun
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« on: January 18, 2016, 09:35:19 PM »

Whats the best way to approach printing multiple lines of text? I can, in theory,extend the Hello World sample code with multiple strings and multiple loops (per string) but I am sure theres a more elegant way?
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Rene_G7400
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« Reply #1 on: January 18, 2016, 10:34:00 PM »

Are you aware of the limitations of the video chip? It can't display several lines of text, except when you update it's registers mid-screen instead of during the vertical blanking interval.
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retroshaun
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« Reply #2 on: January 23, 2016, 09:37:41 PM »

'Sort of' yeah. I was aware of the vblank. I will look into the timings a little...
Whats the best source of info on the video chip?
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gertk
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« Reply #3 on: January 23, 2016, 10:51:53 PM »

Have a look at this thread: http://videopac.nl/forum/index.php?topic=1756.15

Maybe you can pickup some ideas on how to display multiple lines on the Videopac, the quads are used (interleaved) to put multiple characters on one line.

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retroshaun
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« Reply #4 on: January 24, 2016, 08:13:51 PM »

Awesome, thanks!
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Rene_G7400
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« Reply #5 on: January 25, 2016, 09:41:00 AM »

Check this text file for an overview of the registers of the videochip (VDC):
http://home.kpn.nl/rene_g7400/vp_info/vdc.txt
Additional info can be found here:
http://home.mnet-online.de/al/mcs-48/mcs-48.pdf
and here:
http://home.kpn.nl/rene_g7400/vp_info.html
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bwack
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« Reply #6 on: April 29, 2018, 01:09:38 PM »

Thanks ! This is exactly what I was looking for. Been struggeling with getting block of text on the videopac. Been following Sören Gust's dev.asm program (ramcart rom), and it puzzeled me that he used several quads overlayed eachother to get two lines of text. Now it makes sense.

As I'm new to programming on the videopac, do I wait for vblank (call vblank) in a display routine and update the vdc with printchar for every eight vblank or so ? Or wait is it the jmp that is in the interrupt vector table?

A0      : Control

     Bit 0: Enable horizontal interrupt (?)
     Bit 1: 1 = Strobe X,Y beam location into $A4,$A5. 0 = $A4,$A5 latched (*)
     Bit 2: Enable sound interrupt (?)
     Bit 3: Grid control (0=Off/1=On)
     Bit 4: Enable external input overlap interrupt (G7400)
     Bit 5: Foreground (0=Off/1=On) (characters and sprites)
     Bit 6: Dot Grid (0=Off/1=On)
     Bit 7: Grid fill Mode (0=Off/1=On)

I'm working on a sdcart project. Will make another post about that.

Thanks,
Hans / bwack
« Last Edit: April 29, 2018, 01:22:04 PM by bwack » Logged
gertk
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« Reply #7 on: July 03, 2018, 12:51:36 AM »


I'm working on a sdcart project. Will make another post about that.

Thanks,
Hans / bwack

Hi Hans,

What kind of SD cart project will that be ? I have  a prototype with a NXP ARM chip emulating in realtime a Videopac ROM (and more...) games are on SD card. Check this thread: http://videopac.nl/forum/index.php?topic=1756.0
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bwack
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« Reply #8 on: July 04, 2018, 05:26:52 PM »

That sounds really awesome (the romulator).

The SDcart project is based on the Sören Gusts ramcart. My videos explains it better. The snag I have now is printing 'block' of text on the screen. I can have 3-4 lines of text then it seems i get "overflow" meaning the rest comes onto the next screen. Not sure if using interrupts or just wait for timer counting scan lines is the best. If you are interested in my code and project I have everything on the internet, allthough it will probably take the focus away from my question Smiley
https://www.youtube.com/watch?v=L4iWOA2IGnY
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gertk
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« Reply #9 on: July 09, 2018, 07:12:53 PM »

This is what I got running, the data is read from a rom location.

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bwack
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« Reply #10 on: July 25, 2018, 11:47:36 PM »

That is impressive. I see from the post you linked to the timing is very tight. I'll give it another shot.
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