Kakemoms wrote: srowe wrote:
Kakemoms wrote:There are a few bytes in the Kernal that are free or unused, but is it enought...
By my counting there are 118 bytes of unused space (non contiguous). I don't think that would be enough.
Hmm.. no, thats not enough, even compressed.. How did they push JiffyDOS into that ROM.
Well, I finally got my order of 12x2pin userport edge connectors from Taiwan. I though I had ordered 6, but it was 60 pcs in the package... lol.
So I really have to do this now. No need to have 60 connectors laying around. I have looked at the disassembly which is interesting. The schematics Eslapion pointed to also shows that one can do this with 16 I/O lines. The userport has 8+5 general I/O lines from one VIA plus another one that goes through a NOT gate to ATN (so it becomes output only). That can be used to switch the multiplexer. The user port also has two shift register I/O outputs, so a total of 16 lines.
I can draft a schematic once I have read through the disassembly and see if it works. I am missing the 75160/75161, but I can replace them with some 74LS245 on my breadboard to see if I can get it working.. Well, there goes October.
Edit: Here is my suggested V_Link replica. Its going to need new software because the V-Link ROM does not make sense with the available signals on the Userport. It also looks like it can be done without using output 9 on the Userport (which is connected to the serial port). Thus, the IEC should work as normal. Joystick port needs to be unused for this to work.