Instruction Location And Execution Conditions - Omron SYSMAC CS Series Programming Manual

Basic Concepts
Flags
Input flags
• Differentiation Flags
Differentiation result flags. The status of these flags are
input automatically to the instruction for all differentiated
up/down output instructions and the DIFU(013)/
DIFD(014) instructions.
• Carry (CY) Flag
The Carry Flag is used as an unspecified operand in data
shift instructions and addition/subtraction instructions.
• Flags for Special Instructions
These include teaching flags for FPD(269) instructions
and network communications enabled flags
Operands
Operand types
Source Specifies the address of the data
to be read or a constant.
Destination Specifies the address where data
(Results) will be written.
Number Specifies a particular number used
in the instruction, such as a jump
number or subroutine number.
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Instruction Location and Execution Conditions

22
In this context, a flag is a bit that serves as an interface between instructions.
Operands specify preset instruction parameters (boxes in ladder diagrams)
that are used to specify I/O memory area contents or constants. An instruction
can be executed entering an address or constant as the operands. Operands
are classified as source, destination, or number operands.
Example
S
C
D (R)
N
Note Operands are also called the first operand, second operand, and so on, start-
ing from the top of the instruction.
The following table shows the possible locations for instructions. Instructions
are grouped into those that do and those do not require execution conditions.
• Differentiation Flags
Differentiation result flags. The status of these flags are
output automatically from the instruction for all differenti-
ated up/down output instructions and the UP(521)/
DOWN(522) INSTRUCTION.
• Condition Flags
Condition Flags include the Always ON/OFF Flags, as
well as flags that are updated by results of instruction
execution. In user programs, these flags can be specified
by labels, such as ER, CY, >, =, A1, A0, rather than by
addresses.
• Flags for Special Instructions
These include memory card instruction flags and
MSG(046) execution completed flags.
S (source)
D (destination)
Operand
symbol
Source Oper-
and
Control data
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Section 2-1
Output flags
N (number)
Description
Source operand other than control
data (C)
Compound data in a source oper-
and that has different meanings
depending bit status.