amberisvibin / chibi-pc09 Goto Github PK

Didn't know how else to contact you.
Appreciate the 6809 project.

For downtime you might like Questionable Content comic on the net. Latest one - https://www.questionablecontent.net/view.php?comic=4527

Based around a coffee shop in MA with a lot of quirky characters, including robots.

issues with keyboard giving uppercase, but needing lowercase when shift not pressed. may be fixed with a tolowercase function

Benefits:

• proper relative addressing modes
• fully reentrant code
• IRQ stacks entire processor state automatically (Fast IRQ allows customization of exactly what parts of state are stored)
• less cycles per instruction
• position independent code (!!!)
• natively supports 6829 MMU, works almost exactly like proposed TTL MMU (can even do r/rw + x, if it's possible to tell the difference between data read and instruction fetch)
• above features very useful for kernel development

Drawbacks:

• no longer actively manufactured, but is widely available
• max rated freq @ 2mhz (4mhz is possible)(most retro computers didn't get past 2 anyways)
• [MAJOR] no z80 I/O, peripherals will need to be mapped to addr bus (48k RAM? 16 ports of 16 regs, at top of addr?)

NOTE: the motorola documentation is very good

this issue will act as a repo for MPL licensing issues

problems:

• MPL doesnt apply well to schematics and open source hardware
• need to determine how to do documentation license
• MPL must be applied on a file-by-file level (less important)

potential solutions:

• separate licenses for different parts
• split into multiple repos