IBM PC printer adapter schematic

[Tony Duell]

> 
> Tony Duell wrote:
> > Are you in England at the moment? If so, I could probably be convinced to 
> > snail-mail you a copy of the page from the Techref.
> 
> Now sorted out, but thanks anyway (email burp meant I couldn't reply to say I 
> now have it). Ta to those who offered...

I had a quick look in my techrefs last night...

The printer port on the MDA card and the separate printer adapter are 
much the same logically, but there are differences in the actual 
implementation. 

For example, the MDA card inverts some of the status lines from the 
printer using '04 NOT gates. The printer adapter uses '86 XOR gates (XORs 
the siangl wirh '1', basically), presuably because they needed an XOR 
gate to selectively invert one of the address lines to give the 1st/2nd 
adapter address selection. 

-tony