Search found 689 matches

by Martin A
12 Apr 2018 16:32
Forum: What you are doing with Lez's "Free Stuff"?
Topic: Another build
Replies: 27
Views: 31661

Re: Another build

Version 2 video board completed, the new one is the one on the left with the square chip and no cassette tape ports. mk2 video board.jpg Lez sent me (via Dave) some extra parts to improve on the original design. The big change is the move to dual ported ram. The square chip is 8k of DP ram. With the...
by Martin A
04 Mar 2018 22:48
Forum: NEW HARDWARE
Topic: Keyboard replacement
Replies: 45
Views: 62987

Re: Keyboard replacement

Version 2.1 of the keyboard interface. Ok there's logic analyser clips all over it, and it's drawing power from the JTAG header on the CFX-II board, but Bill's latest version of the propeller code allows some USB keyboards to work on the MTX. Looking amazingly similar, the PS2 version of the board c...
by Martin A
01 Mar 2018 21:27
Forum: OFF TOPIC
Topic: ‪Maplin Electronics in administration‬
Replies: 10
Views: 11655

Re: ‪Maplin Electronics in administration‬

I have the 2006 Maplin catalogue on the shelf - its still occasionally useful for checking pin outs.
by Martin A
01 Mar 2018 11:53
Forum: OFF TOPIC
Topic: ‪Maplin Electronics in administration‬
Replies: 10
Views: 11655

Re: ‪Maplin Electronics in administration‬

I hardly use Maplin these days, since the drifted away from electronics into gadgets, there's cheaper places for pretty much everything they sell.
by Martin A
28 Feb 2018 00:03
Forum: What you are doing with Lez's "Free Stuff"?
Topic: Another build
Replies: 27
Views: 31661

Re: Another build

The transistor based setup currently on the board also came from Stardot, page 4 of this thread.

http://stardot.org.uk/forums/viewtopic. ... 4&start=90

The Y output is a straight clone of the original Atom's composite out.
by Martin A
25 Feb 2018 00:40
Forum: What you are doing with Lez's "Free Stuff"?
Topic: Another build
Replies: 27
Views: 31661

Re: Another build

It's a 7 bit Atom printer port - as that's what the OS will expect - I have tied the normally floating 8th bit low. Pictures of the colour output as requested, I've a feeling it's the levels on the Y output that are slightly out, or it's the TV not quite accepting the NTSC colour burst. In text mode...
by Martin A
24 Feb 2018 00:21
Forum: What you are doing with Lez's "Free Stuff"?
Topic: Another build
Replies: 27
Views: 31661

Re: Another build

The board containing the rest of the I/O is now ready for testing. Its got a 6522VIA connected to a parallel printer port, and a BBC Micro style User port on a 20 way header. The atom rom contains code to drive the Printer, on channel A. Channel B is unused and free for the programmer and the user p...
by Martin A
18 Feb 2018 22:21
Forum: What you are doing with Lez's "Free Stuff"?
Topic: Another build
Replies: 27
Views: 31661

Re: Another build

Gosh Martin you have too much spare time! :lol: So much spare time, that I've "finished" this incarnation of the video board. The 3x 74 series chips on the right are there to isolate the 8k video ram when the CPU isn't accessing it. Next to the memory is the VDG, flip flop and 14.4mhx 4x ...
by Martin A
16 Feb 2018 18:21
Forum: NEW HARDWARE
Topic: Keyboard replacement
Replies: 45
Views: 62987

Re: Keyboard replacement

Just for confirmation, the current prototype board connects via the 20 pin header, so there's direct access to: KB9 to KB0 DR0 to DR7 a pulled up connection to Z80 reset Ground And that's it The 5v is picked up from the Port 7 header. There is the posibility of accessing other port 7 signals, or the...
by Martin A
11 Feb 2018 20:31
Forum: NEW HARDWARE
Topic: Keyboard replacement
Replies: 45
Views: 62987

Re: Keyboard replacement

This structure means that USB support can, in principle, be implemented by replacing the cog 1 code by USB code which similarly queues key press and release events in the FIFO buffer. Could the theoretical USB code go in say cog 4, so that either type keyboard could be used depending which is plugg...