Omron SYSMAC CX-Programmer 9, Operation Manual

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Programming Restrictions
Section 2-4
2-4 Programming Restrictions
2-4-1 Ladder Programming Restrictions
There are some restrictions on instructions used in ladder programs.
Instructions Prohibited in
Function Block Definitions Refer to the Programmable Controllers Instructions Reference Manual (Cat.
No. W474)
AT Setting Restrictions
(Unsupported Data Areas) Addresses in the following areas cannot be used for AT settings.
• Index Registers (neither indirect nor direct addressing is supported) and
Data Registers
Note Input the address directly, not the AT setting.
• Indirect addressing of DM or EM Area addresses (Neither binary-mode
nor BCD-mode indirect addressing is supported.)
Direct Addressing of I/O
Memory in Instruction
Operands • Addresses, not variables, can be directly input in Index Registers (both
indirect and direct addressing) and Data Registers.
The following values can be input in instruction operands:
Direct addressing: IR0 to IR15; Indirect addressing: ,IR0 to ,IR15; Con-
stant offset (example): +5,IR0; DR offset: DR0,IR0; Auto-increment:
,IR0++; Auto-decrement: --,IR0
• Direct addressing in instruction operands is not supported for any other
areas in I/O memory.
Restrictions for Input
Variables, Output
Variables, and Input-
Output Variables
(Unsupported Data Areas) Addresses in the following data areas cannot be used as parameters for input
variables, output variables, and input-output variables.
• Index Registers (neither indirect nor direct addressing is supported) and
Data Registers
• Indirect addressing of DM or EM Area addresses (Neither binary-mode
nor BCD-mode indirect addressing is supported.)
Interlock Restrictions When a function block is called from an interlocked program section, the con-
tents of the function block definition will not be executed. The interlocked func-
tion block will behave just like an interlocked subroutine.
Differentiation
Instructions in Function
Block Definitions An instance will not be executed while its EN input variable is OFF, so the fol-
lowing precautions are essential when using a Differentiation Instruction in a
function block definition. (Differentiation Instructions include DIFU, DIFD, and
any instruction with an @ or % prefix.)
• As long as the instance’s EN input variable is OFF, the execution condition
will retain its previous status (the last status when the EN input variable
was ON) and the Differentiation Instruction will not operate.
FB
IL
P_Off
ILC
FB_BODY
Interlocked
Interlock will not
affect instructions in
the function block
definition.