Re: [CAD_CAM_EDM_DRO] Re: Black box again

Tom Eldredge wrote:

> Jon,
>
> I continue to be impressed. I am going to look for a hard disk drive.
>
> Also, could you tell us a little about this 1284 spec?

It is a spec that contains both a communications protocol (which I
don't use very much of) and a way of communicating and signalling
multible devices by remapping some of the parallel port signals.
That is the part that I use. There is also a Microsoft spec, which is not
actually a part of the IEEE-1284 spec, that defines how the register-level
access to a 1284 compatible port should appear on a PC. This is what
I used extensively, although it is nearly impossible to decipher the
document. The key was that it pointed me to some motherboard I/O
chips made by SMS. Their documentation had all the details of how to
put (one of their) standard parallel ports into 1284 mode, and make
it work.

> Could the parallel
> port be accessed using basic poke and peek commands using this spec? Is it
> not a bios spec? Dumb questions?

That's about how I do it in my drivers for EMC. There is an include file
provided with Linux that defines the machine instructions for I/O port
access, like inb and outb, and specifies that they be coded inline, without
a call to a subroutine. This allows for the same efficiencies as writing in
assembly language. But, basically, they are the same as peek and poke.

No, it is not a BIOS spec. I actually TRIED to use the BIOS, which definitely

should have supported the protocol, but I couldn't get it to do anything!
Just totally blank. Maybe that was because my device does NOT adhere
to the full protocol, which would have required a CPU in each board.

Jon