# A92: truth tables

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I recently downloaded "logic" for the ti-92 which is a BASIC program.
Although it is a BASIC program and this is an assembly list, I am typing
to this list for a reason.  The reasons are 1) I can't remember the
ti-basic list until my digest comes up and 2) I also downloaded a
documentation for an assembly program and found it full of wrong answers
to logic circuits.

Now that the reasons are out of the way:

The logic program makes absolutely NO SENSE at all.  The documentation
is small even though it has three pages of words.  I mean, if I didn't
know anything about electronics at all I would explain it more
thoroughly than what the guy who made the program did.  I think he did
mention you had to know some stuff, but even though I know electronics
like the back of my hand, the documenation boggles me.  Instead of using
AND, OR, NOT, BUFFER, XOR, etc. the guy used "affirmation, conjunction"
etc. which makes no sense to me.  I've decided to put some source from
some of my programs here just to piss him off for wasting my time:

BUFFER-output equals input, schematic is a triangle with the output
coming out a vertice and the input at the opposite side:
-|>-  something like that
if TRUE=1 and FALSE=0 the truth table would be:
In Out
0  0
1  1
and the formula would be Out=In

NOT-the output is the opposite of the input, schematic is a triangle
with a circle at the output:
-|>o-
In Out
0  1
1  0
and the formula would be Out=1-In

AND-output is on if the inputs are both on, schematic is a D shape:
=D-
In1 In2 Out
0   0   0
0   1   0
1   0   0
1   1   1
and the formula would be Out=In1*In2

OR-output is on if at least one input is on, schemaic is like the D
shape except the line on the left is curved in, making it look like ))
tis except with lines to connect the curves:
=))-
In1 In2 Out
0   0   0
0   1   1
1   0   1
1   1   1
formula would be Out=-int((In1+In2)/-2)

XOR-output is on if only one input is on, looks like the OR gate except
it has two ) at the input part (really close to each other):
(not drawable on my mailing account)
In1 In2 Out
0   0   0
0   1   1
1   0   1
1   1   0
formula would be Out=abs(In1-In2)

to actually use this in equations you would use "+" for OR, "*" for AND,
and "'" for NOT.  for example "A and B or C and not D" would be
"AB+CD'".  XOR can be written as "AB'+A'B" which is the proper equation.
To find out the proper equations you would make a truth table:
AB O
00 0
01 1
10 1
11 0
and wherever there's a "1" in the "O" (output) you make ANDs.  to make
01=1 in AND, the NOT of 0 is 1 and 1 AND 1 is 1 then A'B which explains
the first 1, and AB' explains the second 1, now put them together
A'B+AB' and you have the truth table explained.

there are easier methods, contact me personally if you want some help (I
can even show you how to make a RAMchip in excel if you want).

-Rob
ICQ:9188921 "No Sol to kill"
e-mail1:rc_ware@hotmail.com
e-mail2:rc_ware@yahoo.com
e-mail3:rc_ware@geocities.com
webpage:http://www.geocities.com/SiliconValley/Haven/4049/index.html

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