🚀 go-pugleaf

In article <19960916.125121.87@werewlf.demon.co.uk>,
dane@werewlf.demon.co.uk (Dane Koekoek) wrote:
 
> In message <1379@assyst.win-uk.net> Dave Pope wrote:

> > Forgive my ignorance, but aren't all Centronics ports
> > bi-directional?
> Nope. All NEW Centronics parallel ports are bi-directional. All from A5000
> onwards are bi-directional. Original Arcs are Uni-directional.
 
> > How else can they handshake?
> Handshake?

Send back simple signals on pins 1, 10 - 17. 
The simpler 'uni-directional' ports tend to use 10 Acknowledge, 11 Busy and
12 Paper End (paper out)
 
> AFAIK the printer driver/computer just sends messages saying "do this", 
> "do that", etc and doesn't care if it's actually done.

Sort of, but then if the printer is only sending back limited info theres
bound to be limited set of responses. The busy signal coming back to the
computer will generate a 'printer offline' message in decent software
though.

> This is how all 
> dot-matrix printers worked... Bi-directional parallel ports mean that 
> software on the computer can monitor the printer and can respond to
> messages
> that the printer sends back, eg codes to say "Out of paper",

As I noted earlier this has always been possible.

> "Paper jam", "Ink cartridge empty", etc.

Yeah, typically 'spoken' by PC/Windoze driver setups in an irritating Merkin
accent. 
 
> > And what about utils. like Laplink? 

> Wouldn't work... Because Uni-directional ports can't go both ways, as the
> name says, so the software just won't work.

Now strangely enough, on PC's the problem was the bios NOT the hardware. Old
PC's which you wouldn't expect to run bi-directionally (and don't for
Windoze etc) will run Laplink.
Anyone feel like having a look at RO3.1 to look at the printer port
routines? or did we have some unidirectional buffer hardware between the
port chip and the physical parallel port in the old machines?

Anyone got a circuit diagram handy?

 

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