Sinclair ZX80 / ZX81 / Z88 Forums

Thanks Bean. Yes I have had many propeller cards over the years. I just haven’t played with one in a couple of years. I’m pretty familiar with Spin but only mildly familiar with Propeller ASM.

I've decided to put the 16K of RAM on my board also.
Can someone explain what I have to do so that it support true Hi-Res mode ?
And maybe why it needs to be done ?

Thanks,
Bean

Wilf goes into considerable detail about the ZX81 video system here

Yes, we know that the pages are full of ? symbols (discussed on here a while ago).

In order for RAM to be hi-res capable, it must output data during both the Z80 read cycle and during the Z80 refresh cycle. So when either /RD is low or when /RFSH is low.

Does that help?

Mark

Does this look correct for 16K that is True Hi-Res compatible ?

P.S. I forgot to show that /RAMCS is tied high too.

Thanks,
Bean

Bean,

I like how you did 16K with only 2 chips. However, have you seen Wilf's circuit for 64K (2 - 16K RAMs) which says it's compatible with all Hi-Resolution formats?

http://www.user.dccnet.com/wrigter/inde ... mories.htm

I had one of my TS1000's modified at some point back to 32K using a 62256 but now I use the 32K memory built in on my ZXPand+.

You're project sure looks interesting!

Tim

A couple questions...
Is there something small I can type-in to see if my 16K memory supports true hi-res ?

Second, should I support atari joysticks/paddles or Wii NunChuk/Classic controller ?

Third, I plan to support VGA, but what about composite video ?

Right now it is going to have:
VGA Text 80x60 64 colors (secondary display, can run ZX81 in fast mode)
VGA Graphic 320x200x4 colors Palette of 64 colors
AY sound emulation (mono)
DAC sound output
Wii NunChuk/Classic controller
TTL Serial In/Out

Everything can be controlled from BASIC using POKE commands.

The module does not have ROM so there are no new/modified commands. This is really geared for assembly-language programmers.

Bean

Bean,

Glad to see this is moving along.. To answer some of your questions/concerns below:

A couple questions...
Is there something small I can type-in to see if my 16K memory supports true hi-res ? - Don't know enough about this

Second, should I support atari joysticks/paddles or Wii NunChuk/Classic controller ? - Atari/C64 9 pin Joysticks are a standard almost on ZX81 and other 8 bit systems - so yes!

Third, I plan to support VGA, but what about composite video ? - Composite video would be great as yours might look better than any hardware or transistor tricks currently in place by some users - always looking for the sharpest screen - so yes!

Right now it is going to have:
VGA Text 80x60 64 colors (secondary display, can run ZX81 in fast mode) - Wow, very cool!
VGA Graphic 320x200x4 colors Palette of 64 colors - Colored graphics - great!
AY sound emulation (mono) - Always a plus if not included on a ZXPand+ already for the user.
DAC sound output - Good
Wii NunChuk/Classic controller - Don't have one, so can't comment.
TTL Serial In/Out - Yes, Yes, Yes!

What do you plan for storage? Tape?

Martin,
Yeah, that is the bad part. This is only an I/O board with an on-board processor. So there is no code "built-in" that the ZX81 can run.
I wish the ZXPand had a pass-thru connector.

I have put a 16K RAM on it just because my board doesn't have a pass-thru either.

Just the be clear, the VGA and/or composite video outputs are secondary. In other words they do NOT show what is on the ZX81 screen. They are like a second screen for the ZX81. You write to them by POKEing values. The one advantage is that you can use the ZX81 in FAST mode which is cool.

Bean

Bean wrote: ↑Tue Jul 30, 2019 2:06 am Just the be clear, the VGA and/or composite video outputs are secondary. In other words they do NOT show what is on the ZX81 screen. They are like a second screen for the ZX81. You write to them by POKEing values. The one advantage is that you can use the ZX81 in FAST mode which is cool.

(Which means no software will work with the hardware. Only the software you create specific for it.)