[Coco] Design Question

RETRO Innovations go4retro at go4retro.com
Mon Mar 27 14:01:32 EDT 2017

Not sure if anyone has an opinion, but thought I would ask:

In most (all?) of my Coco designs, I am putting in FLASH ROM support.  
This requires, at a minimum:

bank register

a bit or two to handle autostart and program mode.  (Say 2 bits).

I find that I have two ways to handle this.

Take, for instance, the CocoNIC cart. I could do two things:

  * Treat the NIC and the FLASH components as separate things. The NIC
    decodes at one base address, the FLASH at another
  * Treat them as a single unit.  NIC registers follow the FLASH
    registers, so to speak (or the other way around).

Advantages of the separated idea:

  * Code can be easily written to handle all of the FLASH portions of
    each cart, without any regard to what else is on the unit
  * nice way to easily add the support to any cart


  * Takes a bit more logic to handle

Advantages of combining:

  * a bit less logic (15 macrocells, in general

Disadvantages in combining:

  * Programming code needs to know more about cart use:
      o If NIC, programming regs are *here*
      o else, if arduino interface, reg are *there*
      o else...
  * Makes it a bit more work to add FLASH to a cart


  * 15 extra macrocells to use for other things.

I am leaning towards maintaining the separation, but thought I would 
canvas for opinions.


RETRO Innovations, Contemporary Gear for Classic Systems

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