Omron SYSMAC C Series User Manual

Introduction to programming
Step 4
Turning the ladder diagram
into PC code
SETE D
When you have finished writing your ladder diagram, the next step is to
encode the diagram into a language the PC can use.
This
language
consists
of
addresses,
instructions,
and
data.
The
addresses
are
locations
in
the
memory
where
instructions
and
data
are
stored.
The
instructions
are
used
to
tell
the
PC
what
to
do
using
the
data
that
follows
each
instruction.
For
example,
let's
consider
a
mini-program
that
ANDs
two
contacts.
Here's
the
ladder
diagram
for
this.
To code this, we first need to specify the memory address from which this
program starts. In this example we'll use 0000 as the starting address. To
this address, an instruction that indicates the beginning of the program
must be written. For the C20, the LD (LOAD) instruction serves this
purpose. In our ladder diagram, the bus bar represents the LD
instruction. Thus this instruction always is used any time the logic line
starts from the bus bar.
On
our
coding
sheet,
next
to
address
0000
we
write
the
instruction
“LD”.
Because the first contact in the AND circuit must be stored as the data of
the
LD
instruction,
we
write
this
down
in
the
“data”
column
on
our
sheet.
In
our example, this data is 0005.
The
next
element
of
the
ladder
diagram
is
the
AND
instruction,
which
we
assign
to
address
0001
in
the
program,
as
shown.
The
data
for
the
AND
instruction
is
the
number
assigned
to
the
second
contact,
in
this case
0006.
On
our
sheet
we
write
this
next
to
the
AND
instruction.
Next we need an OUT (OUTPUT) instruction to output the result of the
ANDed contacts in our circuit. We write this instruction in address 0002,
and
designate
the
output
relay
number
to
which
we
want
this
signal
sent.
We've chosen this relay to be 0500 and have written that as the next entry
on the sheet.
We're finished, except that we always have to tell the PC when a program
is over. So we assign an END statement to address 0003.

Omron SYSMAC C Series Specifications

General

Brand	Omron
Model	SYSMAC C Series
Category	Controller
Language	English