Fredric,
In your 68K Verilog code, I did not see code for the 68k interrupt acknowledge cycle (IACK cycle). The Amiga uses the 68K interrupt acknowledge cycle while the Atari ST (68K) uses both 68K Auto vector interrupts & 68K IACK cycle (for 68901MFP).
I may have missed this in your code, or do you need to still add this support in your 68K core?
I was comparing the ways :
- Taking a picoblaze to emulate a 8051
- Taking a J1 to emulate a 68000.
I would not take a J68 just to make a keyboard controller. :-)
Moreover, emulation is not the exact term since the 68000 "emulation" is heavily HW assisted :
- instruction decoder generates microcode address
- specialized micro instructions help evaluating the effective address
- the ALU is 68000 compatible
On the J68, the bus interface is what is taking most of the room (1000+ LUTs).
Big endian is cool but really resource hungry.
Regards,
Frederic