Commodore 16 / Plus4 Core

[PhantombrainM]

This Topic is for C16/+4 FPGA Questions.

I'll start right away.
The changelog shows that a reset has been improved. What was the original problem?

I have noticed that a reset always erases the memory.
If I press Runstop while doing a reset to land in the built-in machine language monitor and enter M1000, no content can be found. Also you don't get into the Basic with X any more but get a "Break Error".

Just to be clear: Many games have a reset protection built in for this reason. So it is possible that the problem that was fixed was correct. In this case, only switching the C16 on/off or implementing a "hard reset" will help.

regards,
PhantombrainM

[Sorgelig]

Originally C16 core was hard to reset. 50% of resets locked the computer. It had no relation to game protection as it happens on empty computer.

Actually i've added memory erase when i had 16/64KB switch to let Basic recognize 64KB after 16KB. Now it's always 64KB (16KB mode is pretty useless), so probably memory clear is not required anymore.

[Sorgelig]

I've found that C16 need more options..
game like Majesty of Sprites doesn't like NTSC clock. I've thought it won't hurt since PAL and NTSC clocks are very close.
JiffyDOS in C16 gives incompatibilities, so it's better to have switch at least for Kernel ROM.

[Sorgelig]

I'm not familiar with C16. It seems there is a port to switch between PAL/NTSC directly from application. Is it standard C16 feature or just core addition?

[PhantombrainM]

The C16 / Plus4 cannot be switched between PAL and NTSC. You'd need different MOS chips inside for that.

Is it currently running in NTSC mode?

I also noticed some freezing in some games.
"MAC, I" or "Mad Mamba" (all packed from 1988 CST, if you enter LIST).

Maybe that's because of the NTSC mode you mentioned?
By the way, I don't know any NTSC only games. So PAL Mode would be preferred.

If you have questions about the C16, I had one as a kid for eight years. I also have a real one standing here. Don't hesitate to ask me!

As for jumping to the machine language editor while keeping runstop pressed during reset, this is not so important but would be a nice addition.
You could use it to make a memory dump (not so important anymore as alls software is preserved) or to enter a cheat code and then go back into the game.

For Example Aadvark:
https://www.consoledatabase.com/cheats/ ... /aardvark/
(It's not working right now because memory is empty when entering the Monitor.)

regards
PhantombrainM

PS: By the way there is FPGATED V1.1 available and release notes in 1.01 mentions some reset problems have been fixed.
Documents of MISTer say V1.0 is used right now? All in all release notes seem not to be very interesting though. So I don't know if its worth the work to switch: https://hackaday.io/project/11460-fpgated

[Sorgelig]

Ah, thanks for v1.01 news. I will check it.

I will set PAL clock and will provide PAL/NTSC automatic clock switch since TED has specific register (FF07) to switch between NTSC/PAL. So with different kernal ROM (PAL/NTSC) it will work with correct clock.

[Sorgelig]

Update should fix discussed problems.

[PhantombrainM]

Thank you!

Minor bug: If you don't provide a boot.rom, reset from GUI doesn't work anymore. (delete boot.rom from c16 folder)

regards,
PhantombrainM

[Sorgelig]

The issue is in MiSTer binary.
I will fix it.