Vasile Surducan <piclist9 <at> gmail.com> writes:

> 
> Depends. If you take a look here:
> http://www.geocities.com/vsurducan/electro/8255/8255.htm
> you'll see it's read-not. As I remember read-not and write-not signals are
> in opposite phase but that depends hardly on your system timings.
> 
> greetings,
> Vasile
> 
> On 5/29/07, Rikard Bosnjakovic <rikard.bosnjakovic <at> gmail.com> wrote:
> > On 5/30/07, Rich <rgrazia1 <at> rochester.rr.com> wrote:
> > > Hi all.  If I use a 74LS245 bidirectional bus transceiver is the write-not
> > signal the one to the direction control pin?  Or can either the write-not or
> > read-not be used to control the direction?
> >
> > I'm not sure what you mean by "write-not" and "read-not".
> >
> > The 74LS245 has got two pins that control the flow, the DIR (pin 1)
> > and G' (pin 19). The DIR selects if the bus A should move to B, or B
> > to A. The G' effectively turns the whole bus ON or OFF.
> >

Hi, 
The standard pin names for the 74LS245 are Dir and Enable (Motorolla datasheet).
 The link above to 8255.htm has pins DIR and G.  I guess the confusion here is
that  
the /RD pin of 8255 is connected to DIR of 74ls245 in the schematic referenced
by Vasile?

For the 74ls245 Dir controls the direction and Enable will switch the bus
drivers on or off (hi-z state).  Link to the datasheet is
http://www.onsemi.com/pub/Collateral/SN74LS245-D.PDF

Best,

Sergey



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