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1.3 Cautions on Creation of Fundamental Programs

FXCPU Structured Programming Manual

[Basic & Applied Instruction]

1.3.3

Circuits which cannot be created by structured ladder programs and
countermeasures

1. Bridge circuit

A circuit in which the current flows in both directions should be changed as shown in the figure on the right (so
that a circuit without D and a circuit without B are connected in parallel).

2. Coil connection position

• You can program a contact on the right side of a coil. In this case, be sure to program a coil (including a

function or a function block) at the end of the circuit.

1.3.4

Handling of general flags

In some types of sequence instructions, the following flags operate:
<Examples> M8020: Zero flag

M8021: Borrow flag

M8022: Carry flag

M8029: Instruction execution complete flag

M8090: Block comparison signal

M8328: Instruction non-execution flag

M8329: Instruction execution abnormal complete flag

M8304: Zero flag

M8306: Carry flag

*1.

Supported only by FX

and FX

3UC

PLCs.

*2.

Supported only by FX

, FX

3GC

, FX

and FX

3UC

PLCs.

Each of these flags turns ON or OFF every time the PLC executes a corresponding function. These flags do
not turn ON or OFF when the PLC does not execute a corresponding function or when an error occurs.
Because these flags turn ON or OFF in many sequence instructions, the ON/OFF status of flags changes
every time such instructions are executed.
Refer to the examples in the next page, and program a flag contact just under the target sequence instruction.