Parallele port buffering question ....

[rgb]

Hi,

As a newbie I was wondering if it gonna smoke ;-)

I'm planning to use a 74LS244 to bridge between a standard paralelle
port and breadboard (use for prototype of LS IC).

Is it safe, I mean will it stop bad stuff from prototype side to go to
pararallel port ics ?

And also what will happen if I disable output of LS244
I mean how will react standard LS TTL to HiZ input ?

:0)

Thanks

 

[Bullwinkle Jones]

rgb wrote:

Hi,

As a newbie I was wondering if it gonna smoke ;-)

I'm planning to use a 74LS244 to bridge between a standard paralelle
port and breadboard (use for prototype of LS IC).

Is it safe, I mean will it stop bad stuff from prototype side to go to
pararallel port ics ?

And also what will happen if I disable output of LS244
I mean how will react standard LS TTL to HiZ input ?

0)

Thanks

Optoisolators would be the safest bet...

 

[John Popelish]

rgb wrote:
(snip)

And also what will happen if I disable output of LS244
I mean how will react standard LS TTL to HiZ input ?

An open circuit (high Z) is a logic high to any TTL input. Not a very

noise immune high, but a functional high.

--
John Popelish

 

[CFoley1064]

Hi,

As a newbie I was wondering if it gonna smoke ;-)

I'm planning to use a 74LS244 to bridge between a standard paralelle
port and breadboard (use for prototype of LS IC).


Is it safe, I mean will it stop bad stuff from prototype side to go to
pararallel port ics ?

Since you're a newbie, your first piece of advice should be to use a parallel
port on a plug-in ISA card on the computer you were going to throw away, anyway
(at least for the prototyping stage). Parallel ports on motherboards
(especially laptop motherboards) are fairly time consuming and/or expensive to
fix. But if you've got a dozen "throwaway" ISA I/O cards which happen to have
an LPT2 on them, you don't have to worry too much about smoke -- they're
recycled, anyway.

Look at Jan Axelson's website www.lvr.com for plenty of information and links
on parallel port interfacing. Or better yet, buy the Axelson book, "Parallel
Port Complete", which has everything you need, including software examples in
just about every programming language.

Good luck.
Chris