Search found 5198 matches

by 1024MAK
Sun Jun 23, 2024 7:23 pm
Forum: Hardware
Topic: Finally new graphic mode for Lambda 8300
Replies: 9
Views: 139

Re: Finally new graphic mode for Lambda 8300

Some great work there guys :D 8-)

Mark
by 1024MAK
Sat Jun 22, 2024 6:56 am
Forum: Hardware
Topic: Issue 2 CPU fix
Replies: 1
Views: 72

Re: Issue 2 CPU fix

The dead cockroach is determined purely by which ULA version was originally fitted. ULA version 5C102E needs it. All later ULA versions incorporated the logic from the dead cockroach internally, hence it was not required on later machines. Boards that have the dead cockroach normally don’t have the ...
by 1024MAK
Wed Jun 19, 2024 10:53 am
Forum: ZX BASIC
Topic: Alternative to IN to read the keyboard on the zx81?
Replies: 5
Views: 238

Re: Alternative to IN to read the keyboard on the zx81?

A machine code program that reads a Z80 I/O port and returns the result to BASIC is in this post . In that post it's reading a joystick, but it should be easy enough to adapt it to read the keyboard directly. A BASIC program is never going to be fast enough to scan all forty keys. But it should do f...
by 1024MAK
Wed Jun 19, 2024 10:42 am
Forum: Development
Topic: Use of FAST mode... for typing?
Replies: 5
Views: 281

Re: Use of FAST mode... for typing?

It should also be noted that most modern TVs, including the later CRT models, also added 'no signal' detection. Then, when the display cannot detect a valid sync it switches to an internally generated 'no signal' picture. Rather confusingly, this 'feature' may work differently on different inputs of...
by 1024MAK
Wed Jun 19, 2024 8:06 am
Forum: Development
Topic: Use of FAST mode... for typing?
Replies: 5
Views: 281

Re: Use of FAST mode... for typing?

That's an effect of the automatic input selection (on the SCART) system. When the ZX81 was designed and manufactured, it was intended to be used with the CRT TV's of the day. Which typically only had an aerial input socket. Even when TV's started to get SCART sockets, they mostly had manual input se...
by 1024MAK
Tue Jun 18, 2024 3:05 pm
Forum: Hardware
Topic: sinclair spectrum eprom swap gone wrong
Replies: 15
Views: 1249

Re: sinclair spectrum eprom swap gone wrong

Not sure what's going on with the 7805 0V/GND Pin :shock: Has a 0V/GND line been broken somewhere? That kind of fault sometimes can cause a 0V/GND to float up via leakage from the +5V rail. One end (the links side) of R33 also goes to the expansion/edge-connector (25 lower, signal called /ROMCS). Ex...
by 1024MAK
Tue Jun 18, 2024 1:48 pm
Forum: Hardware
Topic: Paper for Alphacom 32 / TS2040 on AliExpress
Replies: 4
Views: 262

Re: Paper for Alphacom 32 / TS2040 on AliExpress

Alphacom 32 print-out
Alphacom 32 print-out
As Moggy says, the paper from www.shopstuff.co.uk is good. This print-out has been printed on a roll from this supplier.

If anyone from the UK wants one or two rolls, I can sell them at cost price plus the cost of postage and packaging.

Mark
by 1024MAK
Mon Jun 17, 2024 12:07 pm
Forum: Hardware
Topic: sinclair spectrum eprom swap gone wrong
Replies: 15
Views: 1249

ZX Spectrum 16K/48K ROM socket

ZX Spectrum 16K/48K ROM socket Pin Function Destination 1 N/C 2 A12 Z80 pin 2 3 A7 Z80 pin 37 4 A6 Z80 pin 36 5 A5 Z80 pin 35 6 A4 Z80 pin 34 7 A3 Z80 pin 33 8 A2 Z80 pin 32 9 A1 Z80 pin 31 10 A0 Z80 pin 30 11 D0 Z80 pin 14 12 D1 Z80 pin 15 13 D2 Z80 pin 12 14 0V/GND 15 D3 Z80 pin 8 16 D4 Z80 pin 7...
by 1024MAK
Mon Jun 17, 2024 11:12 am
Forum: Spectrum BASIC
Topic: Quick hardware check with Peek
Replies: 2
Views: 107

Re: Quick hardware check with Peek

PRINT PEEK 23732 + PEEK 23733 * 256 returns the address of the top of available memory available to BASIC by using a system variable. The BASIC ROM does a test to discover how much RAM is available. PEEK 23733 returns the most significant 8 bits of the address (address lines A8 to A15). In both case...
by 1024MAK
Sat Jun 15, 2024 2:53 pm
Forum: Hardware
Topic: TS1000 Diagnostic Help
Replies: 14
Views: 439

Re: TS1000 Diagnostic Help

Yes, a problem with the market in programmable logic chips is that most 5V or 5V tolerant devices have been discontinued. The main market is now 3.3V devices. To use with 5V TTL (such as the ZX81) means using level shifter chips or finding and adapting the design for one of the 5V or 5V tolerant dev...