Search found 349 matches

by Martin A
18 Apr 2019 22:34
Forum: NEW HARDWARE
Topic: System test rom/Board
Replies: 5
Views: 23

Re: System test rom/Board

Final posting for the day The menu has gained an extra function, seen here from a screen dump in the emulator while testing. Menu.JPG The ram test is now clever enough to spot a duff multiplexer ! RamTesting.JPG And last but not least, the output from the rom test EasterEgg.JPG The question is now, ...
by Martin A
18 Apr 2019 19:58
Forum: NEW HARDWARE
Topic: System test rom/Board
Replies: 5
Views: 23

Re: System test rom/Board

I "draw" my board layout's in Excel. For matrix boards, the layout is as seen from the back, I then just have to connect all of the points with the same name. Pretty much all the wiring on the rom board is either edge connector to chip or chip to chip. The power connections do visit multiple points....
by Martin A
18 Apr 2019 18:07
Forum: NEW HARDWARE
Topic: System test rom/Board
Replies: 5
Views: 23

System test rom/Board

Elsewhere http://www.mtxworld.dk/memorum/viewtopic.php?f=9&t=419 I've mentioned building a board to test a black screening MTX. Rather than drag that thread off topic I've started a new one. The board itself is basically just 2 chips and some configuration jumpers. There's a 32k or larger (e)eprom o...
by Martin A
16 Apr 2019 23:49
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

The wiring on the diagnostic rom board is complete, as is a candidate version of the GAL. The next step is to get a test rom written that will run without using the main ram, but will test it. I've got some video routines working in emulation, once I've got a bit more I'll put together a test image ...
by Martin A
13 Apr 2019 14:25
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

ROM Pin 1 is +5VDC - perhaps you grounded it by mistake and blew something in the power circuit? If you're lucky, it might just be a cap or something, if you're very unlucky, you might have melted a track, either way, the machine can probably be saved, don't bin it just yet I'd echo Dave's comments...
by Martin A
13 Apr 2019 00:15
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

I've chopped up a bit of scrap matrix board and added a 32 pin and 20 pin socket plus some jumpers. to come up with this mock up: rom board idea.jpg A 20 pin 16V8 GAL or CPLD has more than enough capacity to allow for paging in 4 different rom Images from a 32k, 28 pin EPROM or EEPROM. However EPROM...
by Martin A
12 Apr 2019 00:31
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

Unless someone has some pulls from a dead MTX, the only solution I'm aware of for broken roms, is to replace the with EPROM or EEPROM. But that's a one way trip as it means cutting tracks details of how Dave fixed one of his are here: http://primrosebank.net/computers/mtx/repairs/rom/mtx_rom_replace...
by Martin A
10 Apr 2019 20:25
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

Address lines A0-A6 show activity, A7-15 do not. Could this be just the ROM start-up code getting so far within the first 256 bytes before crashing and restarting? But then I should see data on the data bus and I don't. (Well, I often see one edge and sometimes see multiple data on some data lines ...
by Martin A
07 Apr 2019 21:31
Forum: HARDWARE
Topic: Resurrecting an MTX500.
Replies: 51
Views: 245

Re: Resurrecting an MTX500.

Here's a display of the same chip/pin on a working MTX. It does look like you're not getting a true low. Ads00031.jpg The chips don't have to be OKI, I've upgraded both of my MTX500s to MTX512 spec by replacing the OKI 32k parts with 64k, 150ns Samsung KM4164B parts. To make the upgrade work I also ...
by Martin A
26 Mar 2019 00:35
Forum: PROGRAMMING
Topic: Relocating MTX Machine Code
Replies: 5
Views: 96

Re: Relocating MTX Machine Code

I guess that BBC Basic does something similar automatically when you type RUN. BBC Basic has all sorts of nice things built into the assembler that's missing from the MTX Basic. You can: set it up to assemble dynamically and hide the output. Set it to assemble at one address with a totally differen...