Hi, Very interesting read, but it does not say that Laurnce Reeves produced a debugged more efficient version of the 8049 called Hermes. Personally, I would use Hermes over the 8049, it works better in the QL and is still available on Sellyouretro. No - but I only meant to explain that Hermes is us...

More info here :

https://en.wikipedia.org/wiki/Intel_MCS-48

With Micros's like this they offered them in various formats: EPROM piggy back - these have a socket on the back of the chip itself for the program memory EPROM Internal - device has an EPROM for Program memory on board the chip and has a clear window to allow UV erase EPROM OTP - this is the same a...

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.

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 ...

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

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




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




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

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

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...

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.