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Re: Lesson H8- Hello World on the Sega Master System and GameGear

Posted: Sat Jun 04, 2022 9:07 pm
by akuyou
There isn't one, I never read back from VRAM.
Getting a char from the screen like that may work on the SMS, but won't on a bitmap screen like the CPC, so If I need to know what's onscreen I store it in memory somewhere else so I have a solution that is portable across systems.

If you want to do it, You would need to change the VRAM select commands, theres and "or &40" command (or equivalent) which sets the port up for writing, you'd need to remove that and you then should be able to read back from the selected VRAM address

Re: Lesson H8- Hello World on the Sega Master System and GameGear

Posted: Sat Jun 04, 2022 10:06 pm
by Lee
I will try it. It is for checking if the player sprite is colliding with a building or a platform which are
background tiles. This should be quicker than keeping a copy of the screen in the 8K RAM because it is using the hardware. Do you also have a tool to make the correct cartridge checksum in the code footer? I don't know anything about how amstrad screens work because Sega consoles (master system console) are famous and amstrad GX4000 is not. Interestingly the Megadrive is today a commercially viable console and
a new version of it the Megadrive mini 2 announced 2 days ago will be sold.

Re: Lesson H8- Hello World on the Sega Master System and GameGear

Posted: Sun Jun 05, 2022 7:31 am
by akuyou
I never mentioned the GX4000 - but it's clearly famous enough for you to have heard of it.

Oh, and I knew precisely one person with a SMS in the UK in my lifetime, there were four with CPC computers in my street when I was growing up - popularity varies by country you know!

I cover checksums here:
https://www.chibiakumas.com/z80/helloworld.php#LessonH8

Those famicom mini/megadrive mini etc are just cheap FPGA junk quickly produced to cash in on nostalgia - you might as well 3d print a genesis case and stick your Raspberry Pi in it - it would be about as much a 'real megadrive'

Re: Lesson H8- Hello World on the Sega Master System and GameGear

Posted: Mon Jun 06, 2022 5:59 pm
by Lee
You can get different new versions of the megadrive different from FPGA you mention and the version I was thinking of was the genesis on a chip version with a cartridge slot that plays megadrive or genesis cartridges this means it has
all the circuitry of the original megadrive shrinked inside a dedicated ASIC chip whch I suspect is because patents expire after 20 years so different companies can use the valuable design for free. For example as reddit mentions

https://www.reddit.com/r/SEGAGENESIS/co ... 6_genesis/

the HG806 is a genuine gensis on a chip.

The megadrive also contains the master system circuit which need a slot shape convertor to play 8bit games so the master system is still made today.

Re: Lesson H8- Hello World on the Sega Master System and GameGear

Posted: Mon Jun 20, 2022 3:43 am
by Lee
In lesson S10 for the Sega master system https://www.chibiakumas.com/z80/simplesamples.php
I did your draw smiley tile on the sega master system which I got it to work but how do change the smiley tile priority so it appears over any hardware sprite and not below it?Where to toggle the priority bit?