80 Column Video for RC2014

Fuzix will now use this device as a console if detected. There are some rough edges with multiple console support because it turns out the hardware cursor is nailed firmly to the values in the registers used to transfer characters. For a single console this makes total sense. The cursor is sat at the square the next "print stuff" command will use. With multiple consoles however writing to other consoles makes the cursor zip around like crazy.

Probably need to switch to the software cursor approach.

It also turns out that the EF9345 emulator I borrowed from MAME for the emulator is really quite bad once you get beyond a few specific use cases.

The card tests out, after a lot of staring at the circuit diagram and mystery before re-reading the manual. The device actually tristates if the low address bits (aka the select byte we write) is not 0x2X where X is the register and an 'execute' bit. With the right values it appears on the bus and talks.

The video side also seems to work, it's currently rigged up with some resistors and a VGA scaler.

Next stop software. Some of this is fun. The actual device manual was apparently an early work of Abdul Alhazred, shortly before he wrote the Necronomicon. Not only does it make little sense even after hours of arcane study it also shows that the chip really is quite .. strange. The memory layout is peculiar and everything is in 1000 byte blocks with little holes, but all the little holes get collected together as an extra chunk somehow.

Fortunately there is an application note that explains how to program it, and the actual programming incantations shield you from much of the madness. 40 column mode is somewhat weird, with multiple types of character on the same line at once along with various properties that don't necessarily apply the same way to each. So you can mix two colour characters, four colour half resolution characters and 4x2 block graphics on the same line. 80 column seems a lot saner, so I think I will start with 80 column support.