Recent content by gertk

You probably need to swap the ROM, add more RAM and add some storage solution. It does run BBC basic in stock mode AFAIK, but I haven't played with it for ages.

All the traces with the dark spots next to the battery are suspect. Rub or scrape off the silkscreen carefully (a glasfiber pen is ideal for this, just beware of the small bits of glass fiber it leaves behind) and repair the traces if they measure 'open'. Repairing such thin traces can be...

The Exidy Sorcerer came with a Z80 assembler but for more serious programming I recommend crossassembling on a PC (I use Linux and there are several good Z80 assemblers to find) and a serial cable to the CPM machine for testing.

Example

I have updated the GAL files and the schematic so the DISEN signal is delayed. Not perfect yet and the cursor still has to be delayed too.

Seems they are quite scarce.

Ah yes, but now it is public :-)

For the GAL equations and initial schematic: https://github.com/gertk64/BBC_Video_ULA

Making progress, all modes seem to work but still having some issues. First the whole screen seems shifted a bit to the right and on the lefthand side there is a duplicated column from somewhere in the middle of the screen. Palette writes are very time critical so it seems and is not fully...

Yes, for now I leave in the 74LS161 as base clock generator. I added a 74LS157 for selecting RGB between Teletext mode and the other modes. The first GAL is now used for selecting the control register (a 74HC573) and merging the CURSOR, DISEN and RGB signals coming from the LS157 (I think I can...

I was not sure about the CRTCLK part so I tried connecting it directly to the CLK1 (1 MHz) output (just as I did with the 74LS161) also but no change in the behaviour. Just Startup, type a few characters and crash, sound effects etc..

I have used 25 ns ST's which always worked fine for other projects. The newer 15ns Lattice 16V8 I have give an overcurrent error on the TL866 and my older GALprommer on the Atari TT does not recognize them. I found out that the logic compiler on the Atari made a mess of the equations (actually...

Small update: I managed to get the BBC running with a 74LS161 for the clock divider instead of the GAL logic. Probably the GAL did not have enough drive or speed to push out the signals. So far MODE 7 seems to work stable.

Hi, My video ULA recently died in the BBC B here, no clock signals whatsoever, tried it in another BBC and no startup either. I tried replacing it for testing with a GAL 16V8 generating the 4 clock signals(8/4/2/1 MHz), the CRT clock and the throughput/blanking of the SAA5050 RGB signals. So...

Not much: a couple of 6845 registers need to be set up, just like a MDA card (in fact exactly like an MDA card) and you can trigger some extra functions through specific IO ports to enable the graphic functions and RAM pages. After setup the card shows up as 4 k of video ram space with a 80x25...