Re: How do I add firmware to a card?

["David Wilson" <mcs6502@gmail.com>]

mdj wrote:
> Oops, I intended that the Apple II itself would end up being a
> programming device for the uC, such that the uC's firmware could be
> replaced by a host program, thus facilitating upgrades etc.

That is also possible (but would be tricky - the hardware interface for
a programmer may be simple but I am not sure about the actual
programming commands). For example the PIC programmer I use has an
onboard PIC to do the timing critical stuff.

> Of course, this isn't useful functionality in the development cycle,
> but it's handy post-production, since regular users could then "flash"
> their devices to handle the latest improvement.

Actually it is useful during development - no need to take card out of
A2 to program the uC. I have some AT89C51IC2 uC chips which if I read
the data sheet correctly have an onboard boot loader and can be
programmed through the on-chip serial port.

> The approach you mention is also worthwhile, although many uC's don't
> allow code execution from their volatile memory which may cause
> problems. It does open the door for some interesting modifications
> though.

Good point. I forgot many (most?) uC use the Harvard architecture.