Search found 393 matches

by Pr0f
Wed Aug 14, 2019 12:48 pm
Forum: Hardware
Topic: Issue 8 discussions...
Replies: 140
Views: 16700

Re: Issue 8 discussions...

Nasta put a good explanation in the ZX8301 thread, it's to do with I/O access being subjected to the same delays as RAM access when it need not be. In the Issue 6, the HAL does the decoding for the ZX8202, and it can provide DTACK.
by Pr0f
Mon Aug 12, 2019 10:03 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD (Merlin Tonto)

For testing I am using one of those upscaler boards that handles RGB, TTL and various video formats to VGA /LCD. It has OSD that shows you the video spec coming in too - which is quite handy. Works a treat on the QL video output - I think they call them CGA / Arcade to VGA. I am not quite sure what ...
by Pr0f
Mon Aug 12, 2019 8:43 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD (Merlin Tonto)

This doesn't give you composite video, just composite sync.

You could use something like an AD724 to take the R, G and B signals and composite sync and produce composite video and or S-video. I suspect some resistor dividers may be necesary
by Pr0f
Sun Aug 11, 2019 9:05 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD

As Promised, some further updates - a picture of the board with a few sockets in place ready...

IMG_20190811_204916.jpg



also the back of the board, ready for the video mods

IMG_20190811_204746.jpg



Finally - here is an updated pdf with the latest reverse engineering...


opd decoding.pdf
(179.49 KiB) Downloaded 41 times
by Pr0f
Sun Aug 11, 2019 9:01 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD (Merlin Tonto)

Here's a close up of the main PCB back section, where the chip swap and TP3 are:


IMG_20190811_204746.jpg
by Pr0f
Sun Aug 11, 2019 12:33 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD (Merlin Tonto)

TP3 will be a test pad on the PCB - I can get you a close up picture when I get home tonight, showing where that needs to be connected. I plan to make that same modification too. The -5v is required for the RS422 circuit - I can't see it used anywhere else on the board, unless of course it's also pr...
by Pr0f
Sun Aug 11, 2019 8:04 am
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 31
Views: 2883

Re: ICL OPD (Merlin Tonto)

Power and video are towards the bottom of this web page - link below:

https://rwapsoftware.co.uk/oneperdesk/t ... _info.html

I will be putting up an update with some details on the keyboard and main connectors - hopefully later today, and will post more as I continue to delve into it.
by Pr0f
Fri Aug 09, 2019 11:22 am
Forum: Hardware
Topic: Mod on ULA
Replies: 9
Views: 1423

Re: Mod on ULA

The 2 resistors connect to -12v supply and each resistor is in turn connected to the raw data inputs to the ULA from the Microdrive.

Some kind of negative bias to better address the input threshold switching maybe ?
by Pr0f
Mon Aug 05, 2019 7:14 am
Forum: Hardware
Topic: Got my QL today YAY but.....
Replies: 14
Views: 1492

Re: Got my QL today YAY but.....

DeoxIT - That stuff is expensive - but having a few friends in bands - it's excellent for cleaning switches and jack plugs - removes the oxide layer very successfully. I also had something called TIC3000 - which I got from Tandy when we still had those shops here - works amazingly well on house swit...
by Pr0f
Thu Aug 01, 2019 1:20 pm
Forum: General QL Chat
Topic: Oh Hum, The Wiki Has Been Spammed.
Replies: 16
Views: 2181

Re: Oh Hum, The Wiki Has Been Spammed.

NormanDunbar wrote:I'm still 8 bit myself - makes me look a wee bit "jagged" round the edges! ;)

Cheers,
Norm.


Nothing wrong with 8 bit - I'm just finishing off a ZX Nuvo 128 kit, couldn't resist putting a new board in the old rubber speccy case :-)