Well today has been a day of frustration.
I started by picking up the Xilinx board to use as a FLASH programmer. I did have it working at one stage and then started to upgrade the Arduino code to add features.
I couldn't get the code to work no matter what I tried. I then checked the VHDL, the connections between the Arduino and the FPGA and the constraints but no good.
It turned out that the cheap ZIF socket that I got from China was the issue. The pins recede into the housing when you go to plug it into a socket. I soldered pin headers to it - fixed.
Since then (the rest of the day) I have been head down in Hex trying to nut out a character ROM.
I have a ROM (that doesn't include graphics) but it doesn't have the proper descenders on lower case. It is also in a 7 x 8 matrix when it should be 5x7. The actual char cell is 5x7 character in a 6x12 cell. I can add graphics easily so that is not an issue.
I spent hours searching the net for a character ROM image. I found heaps of 8x8 and 8x12 fonts made for a modern systems like windows but not the original. I downloaded several emulators but they all use an 8x12 font and not 6x12.
In reality I can just make the cells 8x8 or 8x12 in hardware but I want to stay with the original specs.
I want to make the cells 6x12 just like the original with 5x8 or 5x9 characters (with descenders) and 6x12 graphics. I also want to just put the graphics in ROM with the characters rather than worry about different timings for ROM characters and combinational logic for graphics.
The solution is to get the facts from the source so I need to know the part number of the chip that generated the characters with descenders and just look up the spec sheet! But dammit, I don't even know the part number.
Now rolling head on keyboard ...klklklklklklklklklklklkliopreeee b,kero