Re: OT: DOS programming EPP

On Tue, 24 Jan 2006 09:28:22 GMT, Robert Baer <robertbaer@xxxxxxxxxxxxx> wrote:


> I followed the guides specified, and after a lot of fiddling,
>discovered what i documented in the program.
> Yes, i was able to determine that an output pin has the
>characteristics of a low power TTL driver (measured output voltage when
>low and sinking 2mA as well as when high and sourcing 2mA).
> And (like i mentioned elsewhere in this thread) when a pin is not in
>an output mode, it acts worse than the input of a high power TTL input
>(and that lasts only for a microsecond, only for the microsecond when
>CONTROL Bit5 is high).

Control Bit5 high sets the data port to high-impedance mode, supporting 8-bit
input (where this is implemented in the hardware). If you DON'T get a high-Z
characteristic, it isn't implemented.

I'm not sure I followed why your C5 is high for only a microsecond - was that
your code?

Be aware also that although the Status port input lines are TTL (and the Data
port when in output mode), the Control port lines are open collector outputs.

> I am giving up, as it seems this MB is hosed; going to an old machine
>and be discreet about the logic, be backwards and shun integration of logic.

Again, I'm not sure whether you issue is with the hardware or your software
implementation.
.

Relevant Pages

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