Step 4-Turning The Ladder Diagram Into Pc Code - 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.
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.
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.
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.