Search found 5101 matches

by 1024MAK
Fri Mar 15, 2024 9:20 pm
Forum: Software
Topic: ZXpand+ JOYCFG.TXT file
Replies: 7
Views: 427

Re: ZXpand+ JOYCFG.TXT file

ZXpand Commander is a file manager/menu/loader program. See this topic... ;-)

Mark
by 1024MAK
Fri Mar 15, 2024 9:16 pm
Forum: Hardware
Topic: ZX Spectrum Issue 6a short
Replies: 17
Views: 477

Re: ZX Spectrum Issue 6a short

The ULA only runs off the +5V. And indeed, the actual supply to the core goes via resistor R34 to pin 13. The ULA has no direct connections to the -5V or +12V supplies. ULA pin 14 just supplies the peripheral interface circuitry. The normal cause of problems with the -5V or +12V supplies, TR4 cookin...
by 1024MAK
Fri Mar 15, 2024 8:43 pm
Forum: Hardware
Topic: Spectrum modded / composite question
Replies: 19
Views: 707

Re: Spectrum modded / composite question

Well, with only seven 4116 DRAM chips fitted, it will do something, but no, it will not run BASIC.

The ULA should however produce a picture. What you get depends on which chip is missing. The effect being different depending on which one it is that is missing.

Mark
by 1024MAK
Fri Mar 15, 2024 1:37 pm
Forum: Hardware
Topic: Atari joystick without ZXpand+
Replies: 33
Views: 1064

Re: Atari joystick without ZXpand+

BASIC always uses its own ROM routines to read the keyboard. At the lowest level, this is the Z80 processor using the Z80 machine code IN instruction. Each keyboard half row has its own I/O address. The data returned is one byte, but only five bits are keyboard data. Hence it takes eight IN instruct...
by 1024MAK
Thu Mar 14, 2024 5:04 pm
Forum: Hardware
Topic: Atari joystick without ZXpand+
Replies: 33
Views: 1064

Re: Atari joystick without ZXpand+

I was looking at the schematic and wondering how external keyboards work via the edge connector if there is no access to the five KBD lines that go to the ULA. Is the ROM checking for keypresses? I haven't yet tripped over how this actually works yet. That's an entirely new subject... The simple an...
by 1024MAK
Thu Mar 14, 2024 4:56 pm
Forum: Hardware
Topic: Atari joystick without ZXpand+
Replies: 33
Views: 1064

Re: Atari joystick without ZXpand+

Moggy wrote: Thu Mar 14, 2024 4:36 pm I do Have a Kempston but this I seem to remember, unlike what Mark describes, has the extra tangs as used on a Spectrum interface.
As far as I am aware, all the later Kempston versions did have the longer ZX Spectrum edge-connector sockets.

Mark
by 1024MAK
Thu Mar 14, 2024 4:53 pm
Forum: Hardware
Topic: Atari joystick without ZXpand+
Replies: 33
Views: 1064

Re: Atari joystick without ZXpand+

msknight wrote: Thu Mar 14, 2024 4:45 pm I had read that, but Kelly's, "last active" came up with just a dash, so I concluded hadn't been around for a while.
Still active, has visited this week.

Mark
by 1024MAK
Thu Mar 14, 2024 3:31 pm
Forum: Hardware
Topic: Atari joystick without ZXpand+
Replies: 33
Views: 1064

Re: Atari joystick without ZXpand+

There was no particular joystick interface that was popular for the ZX81, hence there is no real "standard". Just various interfaces that don't have much in the way of software support, most of which were forgotten about long ago. Kempston produced joystick interfaces for the ZX Spectrum, but used t...
by 1024MAK
Wed Mar 13, 2024 7:32 pm
Forum: Hardware
Topic: Spectrum modded / composite question
Replies: 19
Views: 707

Re: Spectrum modded / composite question

These days, it's whatever you can get hold of that work. And yes, you can mix and match. Sinclair used various makes/brands of 4116 DRAM or equivalents. Alternately, use 4164 type and modify the board to suit these. Whatever you use, they do need to have an access time of 150ns or faster. Slower par...
by 1024MAK
Wed Mar 13, 2024 3:21 pm
Forum: Hardware
Topic: Spectrum modded / composite question
Replies: 19
Views: 707

Re: Spectrum modded / composite question

ULAs seem harder to come by. Original 'spare' ULA chips ran out years ago. Only used ULAs come up occasionally. However, there are replacement ULA modules. But they are in a limited supply, and are not cheap. Nebula - Scroll down on this page . vLA82 - link From my understanding I'd need a clear vi...