Search found 3584 matches

by 1024MAK
Sat May 08, 2021 12:21 am
Forum: Hardware
Topic: Bad 12v line ISSUE 6A with only 5v RAM
Replies: 11
Views: 559

Re: Bad 12v line ISSUE 6A with only 5v RAM

If the border stops blinking if reset is held active, then it’s the Z80 writing to the ULA I/O port. I don’t think a DIVMMC can be used. The DIVMMC is based on the technology from the divide. The divide has 8k bytes of ROM and 8 k bytes of RAM in the bottom 16k of the Z80 memory map, not the needed ...
by 1024MAK
Sat May 08, 2021 12:11 am
Forum: Hardware
Topic: Bad 12v line ISSUE 6A with only 5v RAM
Replies: 11
Views: 559

Re: Bad 12v line ISSUE 6A with only 5v RAM

The ZX Spectrum does not do grey, that will be non-bright white (the border can’t do any of the bright colours).

Strange that it’s blinking to green.

Mark
by 1024MAK
Fri May 07, 2021 8:51 am
Forum: Hardware
Topic: Bad 12v line ISSUE 6A with only 5v RAM
Replies: 11
Views: 559

Re: Bad 12v line ISSUE 6A with only 5v RAM

Z80 pin 20 is /IORQ and is normally high unless an input/output (I/O) device is being accessed. In an unexpanded ZX Spectrum, there is only one I/O device - the ULA (the register/outputs for border colour/tape mic/speaker and the input port for tape ear and keyboard). If the Z80 is not running the c...
by 1024MAK
Thu May 06, 2021 1:15 pm
Forum: Hardware
Topic: Yet another 48K restoration (no tape loading sound on speaker)
Replies: 7
Views: 4175

Re: Yet another 48K restoration (no tape loading sound on speaker)

Thanks for (eventually) replying :lol: Good to know that you have fixed and sorted out the issues. You can select notifications in the user control panel. Yes, despite Sinclair being known for using whatever components that were available at the right price, for some reason people think that the typ...
by 1024MAK
Wed May 05, 2021 5:35 pm
Forum: Hardware
Topic: ULA revision
Replies: 6
Views: 226

Re: ULA revision

The ULA does not have any memory location that can be accessed with PEEK. And the ZX81 BASIC does not have either the IN (INP) function or the OUT command. And even if it did, that would not tell you which ULA version is in the machine. As Paul says, the last version generates the back porch part of...
by 1024MAK
Tue May 04, 2021 8:03 am
Forum: Emulators
Topic: Eightyone - using a joystick
Replies: 6
Views: 389

Re: Eightyone - using a joystick

Spinnetti wrote: Mon May 03, 2021 11:22 pm Ah, thanks.. there's a checkbox that says it supports the zxpand.. too bad it doesn't pick that up... How can I contact/beg the maker of the zxpand to make some more? :)
sirmorris

But he’s not been on here for a while... :-(

Mark
by 1024MAK
Mon May 03, 2021 6:57 pm
Forum: Development
Topic: UDG - Just UDG...
Replies: 18
Views: 723

Re: UDG - Just UDG...

On a real ZX81/TS1000, to get UDG, you need a memory chip to supply different data compared with the data in the BASIC ROM chip. Until the ZXpand and Andy’s UDG board, the only way (*) was to buy/make an internal ROM/RAM board and fit it in place of the BASIC ROM. They could have the BASIC ROM, a cu...
by 1024MAK
Mon May 03, 2021 12:51 pm
Forum: Hardware
Topic: Bad 12v line ISSUE 6A with only 5v RAM
Replies: 11
Views: 559

Re: Bad 12v line ISSUE 6A with only 5v RAM

Tr4 measured from back to front 0v, 5v and 9v (just 0.05v less than the input vcc) Tr5 measured 4.33, 4.2, 4.5v. These voltages do not make sense. TR5 emitter is connected to the +5V supply, so should be the same voltage as the +5V regulator output (+4.75V to +5.25V). If the +12V rail is very low, ...
by 1024MAK
Sun May 02, 2021 6:59 pm
Forum: ZX BASIC
Topic: Can't make anything fit into 1K... or is it me?
Replies: 18
Views: 1027

Re: Can't make anything fit into 1K... or is it me?

This program shows how small the program has to be if you use a large amount of the screen (and hence the display file becomes large):

Code: Select all

1 PRINT CHR$ (RND*25+38);
2 IF PEEK 16442=INT PI THEN GOSUB 9
3 GOTO SGN PI
9 SCROLL
10 SCROLL
11 PRINT AT 19,SGN PI;
12 RETURN
Mark