Re: Bidirectional parallel port

[Rubywand <rubywand@swbell.net>]

haubi@geocities.com writes ...
> 
> ....
> Does anybody know how to *read* from a printer interface, something 
> like peeking $C090? ....
>

     Our home-brew interface (in Slot 1 of an Apple II+) uses $C090 to 
write data to the printer and to read status signals. The status signals 
we read are ...

Bit 0  Error? (0= Yes, printer is Off-line or disabled; 1= No)
  This signal is via pin 32 of printer cable.

Bit 1  Printer initialized? (1= Yes; 0= No, there has been a
  recent Reset, need to do printer init sequence)
  This signal is generated on the board. It may not be present
  on some other interfaces. 

Bit 7  Ready? (0= Yes, ready to accept data; 1= No)
  This signal is via pin 11 of printer cable. (Often, it is named
 "Busy". A logic "1" = busy, not ready to accept data.) 

     The cable pin info comes from a Star Micronics Gemini-10X manual. 
(Hey, here's our registration card! There's a place for checking which 
magazines we read regularly: Apple Orchard, Dr. Dobb's Journal, ... .) 
The Gemini was fairly compatible with most printers of the time; so, the 
cable info is likely to fit a number of other printers.

     To obtain status information, PEEKing 49296 ($C090) would work fine 
for an interface like the one described above placed in Slot 1.    

 
Rubywand