On Wed, 09 Jun 2010 19:39:42 -0500, flipper wrote:

On Wed, 09 Jun 2010 18:05:27 -0500, John Fields
wrote:

Diode nightmare, or heaven, depending on your feeling about diodes

Unless I misinterpreted the schematic you can save 8 diodes right off
the bat by just tying OUT1 high.

Actually, out1 is not required, as state zero is when the other seven
outputs are off.

If there's not a loading problem you can save more by using A0-A2 in
lieu of various 'decoded' outputs. For example, OUT2 can be just 3
diodes from A0-A1-A2. OUT3 can be 3 diodes from Y2-Y3-A2 and OUT4 can
be 2 diodes from Y3-A2, etc. That saves another 10 diodes.

Yes, a fair bit can be done straight from truth table and inverted ABC
lines.

It might be better to make your own logic decoder, rather than going
through a 238 first, but I didn't sit down and try designing one to
see.

It started as an exercise to see if there was a standard MSI logic
part that could do the 3 to 7 decode with lower lines staying on. I
didn't notice the extra Y0 output when I first clapped eyes on that
sea of diodes All I saw was diodes, lots of 'em!

Grant.
--
http://bugs.id.au/

"John Fields" schreef in bericht
...

Hmm... Don't like that bag of diodes. If you don't want to program a device
and can neglect possible glitches, some simple 14 pins gate chips will do
the trick. An old LS08 and an LS32 or their newer counterparts will do.

c ----------+ __
__ +-|=|
b ---|=| |1 |--- s1
|1 |---+-|__|
a ---|__| |
+-------- s2
__
c ---| | __
|& |-----|=|
b ---|__| |1 |--- s3
+--|__|
a ---------+

a ------------------- s4
__
c ---| | __
|& |-----|=|
a ---|__| |1 |--- s5
+--|__|
|
+--------- s6
__ |
b ---| | | __
|& |--+--| |
a ---|__| |& |--- s7
+--|__|
c ---------+
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

petrus bitbyter

On Fri, 11 Jun 2010 04:02:13 +0200, "petrus bitbyter"
wrote:

"John Fields" schreef in bericht
.. .

Hmm... Don't like that bag of diodes. If you don't want to program a device
and can neglect possible glitches, some simple 14 pins gate chips will do
the trick. An old LS08 and an LS32 or their newer counterparts will do.

c ----------+ __
__ +-|=|
b ---|=| |1 |--- s1
|1 |---+-|__|
a ---|__| |
+-------- s2
__
c ---| | __
|& |-----|=|
b ---|__| |1 |--- s3
+--|__|
a ---------+

a ------------------- s4
__
c ---| | __
|& |-----|=|
a ---|__| |1 |--- s5
+--|__|
|
+--------- s6
__ |
b ---| | | __
|& |--+--| |
a ---|__| |& |--- s7
+--|__|
c ---------+
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

petrus bitbyter



Yep. Actually didn't we have this very same problem presented here a
year or so ago?

...Jim Thompson
--
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