Atari 2600 / VIC 20

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Lroby74
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Re: Atari 2600 / VIC 20

Postby Lroby74 » Fri Feb 15, 2019 10:53 pm

slingshot wrote:Yes


Did it, thank you!

Now it's time to create C16.ROM :)

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DrOG
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Re: Atari 2600 / VIC 20

Postby DrOG » Sun Mar 10, 2019 6:41 pm

Hi!

This weekend I noticed that the video out of the Atari 2600 core shows some colors wrongly in case of PAL ROMs if scanlines are set to 25 or 50%. Usually I connect my MiST over SCART to the display, but this time tried component. Over VGA (only NTSC ROMs are compatible with my TV using this connector) no such decoloration, but scanlines are barely visible over blue background. See attachments taken from Seaquest.

Cheers: Gábor
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Re: Atari 2600 / VIC 20

Postby slingshot » Tue Mar 12, 2019 9:01 am

The reduced scanline modes are discarding some bits from the RGB output, and sometimes it can transfer to some different colors, as I see. Will check once...

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Re: Atari 2600 / VIC 20

Postby DrOG » Tue Mar 12, 2019 1:16 pm

slingshot wrote:The reduced scanline modes are discarding some bits from the RGB output, and sometimes it can transfer to some different colors, as I see. Will check once...

Thank you in advance! Not urgent at all, I use mainly SCART connector in case of my main screen as it's very picky in aspect of non-standard resolutions/refresh rates over VGA as mentioned earlier.

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Re: Atari 2600 / VIC 20

Postby Lroby74 » Tue Apr 02, 2019 10:19 am

A friend of mine (Antonino or Nino for friends Porcino) started very recently to study Verilog and VHDL, and added in the Vic20 core the ability to read an audio file (for now) from the Mistica EAR port, his goal would be to become expert enough to add full support for TAPs (including the various Datasette keys) in the C64 core.

He released a small demonstration video:
https://www.facebook.com/groups/2955017 ... 625401460/
Last edited by Lroby74 on Fri May 03, 2019 8:26 am, edited 1 time in total.

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Re: Atari 2600 / VIC 20

Postby DrOG » Tue Apr 02, 2019 12:41 pm

Lroby74 wrote:A friend of mine started very recently to study Verilog and VHDL, and added in the Vic20 core the ability to read an audio file (for now) from the Mistica EAR port, his goal would be to become expert enough to add full support for TAPs (including the various Datasette keys) in the C64 core.
He released a small demonstration video:
https://www.facebook.com/groups/2955017 ... 625401460/

It would be really nice! Mistica's EAR port can be easily reproduced on a daughterboard for the MiST (in fact I believe Mistica utilized the original schematic of V6Z80P, as they are the same - BC846 is the SMD version of BC548, see attachments).

We recently try to modify the original circuit to accept lower signal levels (perhaps line-in voltages as well), see details in another topic:
viewtopic.php?f=115&t=30124
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Re: Atari 2600 / VIC 20

Postby slingshot » Thu May 02, 2019 7:55 pm

I assumed VIC-20 is complete, I was wrong:

https://github.com/gyurco/VIC20_MiST/releases/tag/1.7

The horrible audio distortion is fixed, also @nippur72 rewrote the sound generator. TAP support is added.

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Re: Atari 2600 / VIC 20

Postby DrOG » Fri May 03, 2019 4:41 am

THX!!! :cheers: Gonna try it this weekend!

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Re: Atari 2600 / VIC 20

Postby DanyPPC » Fri May 03, 2019 6:15 am

Really great update ! :cheers:

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Re: Atari 2600 / VIC 20

Postby DanyPPC » Fri May 03, 2019 7:55 am

Vic20 core lacks an option like C16/C64 Cores to load a standard kernal, so I have to delete my VIC20 JiffyDOS rom from SD card if I want to load tapes.

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Re: Atari 2600 / VIC 20

Postby Lroby74 » Fri May 03, 2019 5:57 pm

DanyPPC wrote:Vic20 core lacks an option like C16/C64 Cores to load a standard kernal, so I have to delete my VIC20 JiffyDOS rom from SD card if I want to load tapes.

ATM, you can rename or move into a subfolder Vic20.rom file when you need to load TAPs :)

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Re: Atari 2600 / VIC 20

Postby vebxenon » Tue Jun 04, 2019 12:28 pm

E7 mapper added thanks to Slingshot :D :cheers: :cheers:

https://github.com/mist-devel/mist-bina ... ores/a2600

"E7 - M-Network cart (Bump'n'Jump, Burgertime), use .E7 extension"
Just a computer and videogame lover :)

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Re: Atari 2600 / VIC 20

Postby DanyPPC » Tue Jun 04, 2019 2:11 pm

Burger time don't move ! :shrug:

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Re: Atari 2600 / VIC 20

Postby slingshot » Tue Jun 04, 2019 5:32 pm

DanyPPC wrote:Burger time don't move ! :shrug:

It needs "B" difficulty setting (same in Stella, so not a core bug).

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Re: Atari 2600 / VIC 20

Postby DanyPPC » Tue Jun 04, 2019 7:04 pm

Ah, ok. You are right :wink:

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Re: Atari 2600 / VIC 20

Postby NML32 » Tue Jun 04, 2019 8:19 pm

I'm happy to see the Atari 2600 core getting updates. :D

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Re: Atari 2600 / VIC 20

Postby slingshot » Tue Jan 14, 2020 9:06 am

Timer fix season...
Looks like a small error in RIOT caused unstable video in many games (Star Wars acrade, Espian, Tapper, ...). And nobody noticed that Haunted House and Video Pinball don't work properly?
Attached a fixed core, please test it, hope I didn't break something else. If not, I'll put it on mist-binaries.
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Re: Atari 2600 / VIC 20

Postby vebxenon » Tue Jan 14, 2020 4:11 pm

slingshot wrote:Timer fix season...
Looks like a small error in RIOT caused unstable video in many games (Star Wars acrade, Espian, Tapper, ...). And nobody noticed that Haunted House and Video Pinball don't work properly?
Attached a fixed core, please test it, hope I didn't break something else. If not, I'll put it on mist-binaries.


It works very well!!! And now video is too stable :cheers: :cheers:
Just a computer and videogame lover :)

- Atari Jr 2600 clone
- Atari 7800 Peritel
- Atari XEGS
- Atari Lynx II
- Atari Jaguar
- MiST Board

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Re: Atari 2600 / VIC 20

Postby DanyPPC » Tue Jan 14, 2020 4:55 pm

Well done !!!

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Re: Atari 2600 / VIC 20

Postby slingshot » Fri Jan 17, 2020 12:27 pm

Some background of the Haunted House bug:
At some point, the programmer intended to execute a
SBC #$0F
instruction.
However during the process from the brain to the keyboard, it became a
SBC $0F
And this, instead of subtracting $0F from A, is subtracting the value read from zero page address $0F from A.
$0F is in the TIA address space, but register $0F exists only for writing. Reading from this address will put nothing on the bus, so the CPU "sees" the last value read from it (probably latched somewhere). And what was the last value? $0F of course, the second byte of the instruction. So at the end, SBC #$0F and SBC $0F is identical on an Atari2600.

I found it interesting, maybe someone else, too.


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