!
!
39
3-3-2
PC Modes
There are two PC operating modes that are set from the Programming Con-
sole: RUN and PROGRAM.
RUN mode is used for normal program execution once the program has
been input. In RUN mode, input terminal status is read into the PC and out-
put terminals are updated according to program execution results.
PROGRAM mode is used for programming operations to input and debug the
program when setting up the control system and for data access and manip-
ulation once a control system is running. The program is not executed in
PROGRAM mode.
When the PC is turned on with the Programming Console attached, the
mode switch on the Programming Console will determine the initial operating
mode.
If the Programming Console is not attached, the PC will always start in RUN
mode and the program will be executed immediately.
If the Programming Console is attached after the PC is already turned on, the
current mode will continue regardless of the setting of the Programming Con-
sole mode switch.
WARNING
Always confirm that the Programming Console is in PROGRAM mode when
turning on the PC with a Programming Console connected unless another mode
is desired for a specific purpose. If the Programming Console is in RUN mode
when PC power is turned on, any program in Program Memory will be executed,
possibly causing a PC-controlled system to begin operation. If the START input
on the CPU Power Supply Unit is ON and there is no device connected to the
CPU, ensure that commencing operation is safe and appropriate before turning
on the PC.
WARNING
Do not leave the Programming Console connected to the PC by an extension
cable when in RUN mode. Noise detected via the extension cable can enter the
PC, affecting the program and thus the controlled system.
3-4
Basic Programming
3-4-1
Terminology
There are basically two types of instructions used in ladder-diagram pro-
gramming: ladder instructions that correspond to the conditions on the ladder
diagram and right-hand instructions that are used on the right side of the lad-
der diagram and are controlled by the ladder instructions. Ladder instructions
are used in instruction form only when converting a program to mnemonic
code.
Most instructions have at least one or more operands associated with them.
Operands indicate or provide the data on which an instruction is to be per-
formed. These are sometimes input as the actual numeric values, but are
usually the addresses of words or bits that contain the data to be used. For
instance, a MOVE instruction that has word 00 designated as the source op-
erand will move the contents of word 00 to some other location. The other
location is also designated as an operand. A bit whose address is designated
as an operand is called an operand bit; a word whose address is designated
as an operand is called an operand word. If the actual value is entered as a
constant, it is preceded by # to indicate that it is not an address.
Startup Mode
Basic Programming
Section 3-4