18 Dec
2009
18 Dec
'09
7:28 p.m.
On Thursday 17 December 2009, Tony Duell wrote:
'Getting away with it' is something I will do for quick hacks on my own
bench, but not for stuff likely to be used by others, or stuff I depend
on.
The thing is that I suspoect (without reading the
data sheets) that
most microcontrollers can't meet the HPIB spec on their port pins,
you need to put something between the port and the 24 pin
microribbon connector. Might as well be one of the chips designed
for the purpose.
In any case I have an objection to linking an expensive (probably)
custom-programmed (certianly) part to an external connector that's
going to be linked to $deity-knows-what. Much easier to replace a
buffer chip if somethign goes wrong than replace the
microocontroller and have to program it again.
I see "meeting specs" as a potential problem (though if it's the only
device on the bus besides the controller, , you can probably "get away"
with it). However, the microcontroller may easily be
less expensive to
replace than the HPIB buffer (especially if you compare the price for
each new/NOS).
Possibly. I said 'easier', not 'cheaper' though. The point being that the
buffer chip doesn't have to be programemd, so it can be replaced by
somebody who doesn't have a programmer for whatever microcontroller is
used. Most modern microcotnrollers (at least ones with enough I/O for
this) come in a surface-mount package, the buffers certainly were
available in DIPs (and could be socketed).
Repair cost != component cost...
-tony