Logic Symbols
Analog and Digital In a Crestron
World
For Crestron programming purposes
– Digital is single digit Binary (1/0, On/Off)
– Analog is 16 bit Binary, Decimal or Hex
Digital Decisions
• Digital decisions are made by logic
“elements” or “gates”
• A logic element will have it’s output state
determined by the state of it’s inputs
• The most basic gates are:
• AND
• OR
• NOT
OR +
A
B
A+B
This gate may have 2 or more inputs
The output is “true” when any input is true
The + sign represents OR
A + B means A or B
.
AND
A
B
A.B
This gate may have 2 or more inputs
The output is “true” when ALL inputs are true
The
. sign represents AND
A . B means A AND B
______
NOT
_
A
A
This gate has only 1 input
This is sometimes called an INVERTER
The output is true when the input is not true
___
The
represents NOT
_
A means NOT A
Truth Tables
• Truth Tables are useful in determining the
action of a logic symbol
• A truth table shows all combinations of
inputs and the corresponding output for
each.
AND Truth Table
Input
A
0
Input
B
0
Output
A AND B
0
0
1
0
1
0
0
1
1
1
OR Truth Table
Input
A
0
Input
B
0
Output
A OR B
0
0
1
1
1
0
1
1
1
1
NOT Truth Table
_
A A
0 1
1 0
Make your own Truth Table or
Logic Statement
• Given a scenario, if you can create a truth
table or a “logic statement”, it will help to
create the program logic.
Example: You want the DVD power on to
work only before 11:00 at night so the kids
don’t stay up late. You also want the DVD
power button to be smart, meaning not to
power off if you mean to leave it on.
Assumptions
• You have a signal from the built in clock
that tells you it is after 11:00 (ELEVEN)
• You have a signal from i/o port 1 that tells
you the DVD Power is On (DVD_ON)
• The touchpanel signal from press-join 10
is called DVDPOWERON
Start a statement
You need to send out the power signal to
the DVD player when it is before 11:00
and someone pushes the DVD power on
button and the DVD player is off.
Make the statement more of an equation
DVDPOWER = DVDPOWERON and NOT
DVD_ON and NOT ELEVEN
Truth Table
DVDPOWER = DVDPOWERON and NOT DVD_ON and NOT ELEVEN
DVDPOWERON
DVD_ON
ELEVEN
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
DVDPOWER
Truth Table
DVDPOWER = DVDPOWERON and NOT DVD_ON and NOT ELEVEN
DVDPOWERON
DVD_ON
ELEVEN
DVDPOWER
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
1
1
0
1
0
1
1
0
0
1
1
1
0
Draw the Logic
• From statement or truth table or both,
develop the logic diagram
DVDPOWERON
ELEVEN
DVDON
NOT
NOT
AND
DVDPOWER
Program the logic
Use a Truth Table Symbol
• Crestron has a truth table symbol
• It may be easier than building your own
logic
• You still have to understand the logic to
make the truth table correct