Re: Disk ][ controller PROM

[Alex Freed <alex_news@mirrow.com>]

Steven Hirsch wrote:
> DIP package PROMs. When my eBay purchased Advin Pilot 143 programmer 
> arrived, I read the PROMs and, unless the programmer is defective, all 
> of them are programmed as a chip full of 0fh values.  This is not 
> correct and would explain the misbehavior.

My money is on the defective programmer. Can't imagine how the chips can
get to this state if they were ever good.

> I was interested in reading a known-good PROM as a reality check, thus 
> the questions about the A2 disk controller.

Reading a ROM/PROM is a no-brainer. If you apply the power and ground to
the right pins, nothing within reason you can do will damage them. All 
you need is select some bit combination on the address lines, apply the
chip select (active low in most cases) and see what's on the outputs.
The only issue is that you need some pull-up resistors on the outputs
if they are open collector which is the case with many bipolar ROMs.

-Alex.