more p-port 101 was Re: troubleshooting help

Alan,

This is not correct. I had to go back and check Zhahei Stewarts' P-
port FaQ, just to be sure: http://www.lvr.com/files/ibmlpt.txt

The p-port bytes are as I posted: Data, Status, and CONTROL (not
command); at base, base+1, and base+2, respectively.

In the classic spp (standard p-port) the data is an output byte, the
status is 5 bits of an input byte, and the control port is 4 bits of
open collector, which can be used for either/both input and output.
Pin 17 can be "flakey" on some boards... (the data byte of most p-
ports of the last several years is bidirectional, even in SPP mode.
The "direction" of this Data byte is set with a bit in the Control
byte)

There ARE some(very few, and older) port cards which have the control
byte at base+1, but this is NOT a correct implementation of the IBM
design.

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi Rick,
>
> The CMD port is at +1, IE, 889.
>
> The bit assignments are:<snip>