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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
6 What to Understand before Programming
6.5 General Rules for Applied Instructions
6.5.3 Handling of operation error flag
When there is an error in the applied instruction configuration, target device or target device number range and an
error occurs while operation is executed, the following flag turns ON and the error information is stored.
1. Operation error
• When an operation error has occurred, M8067 turns ON and D8067 stores the operation error code number.
•In the FX
3U/FX3UC PLCs, D8315 and D8314 (32 bits in total) store the step number in which the error has occurred.
When the error occurrence step number is up to 32767, the error occurrence step can be checked also in D8069
(16 bits).
• In the FX
3G PLC, D8069 stores the error occurrence step number.
• If another error occurs in another step, the stored data is updated in turn to the error code and step number of the
new error. (These devices are set to OFF when errors are cleared.)
• When the PLC mode switches from STOP to RUN, these devices are cleared instantaneously, and then set to ON
again if errors have not been cleared.
2. Operation error latch
• When an operation error has occurred, M8068 turns ON.
•In the FX
3U/FX3UC PLCs, D8313 and D8312 (32 bits in total) store the step number in which the error has occurred.
When the error occurrence step number is up to 32767, the error occurrence step can be checked also in D8068
(16 bits).
• In the FX
3G PLC, D8068 stores the error occurrence step number.
• Even if another error has occurred in another step, the stored data is not updated, and remains held until these
devices are forcibly reset or until the power turns OFF.
• When the error occurrence step is up to the 32767th step, the error occurrence step can be checked in D8068 (16
bits).
6.5.4 Handling functions of extension flag
In some applied instructions, the function can be extended by combining a specific special auxiliary relay determined
for each applied instruction. An example is explained below.
- When X000 turns ON, this instruction exchanges the
contents of D10 and D11 with each other.
- If M8160 has been driven before the XCH instruction and
the source and destination of the XCH instruction are
specified to the same device, high-order 8 bits and low-
order 8 bits are exchanged with each other inside the
device.
- For returning this XCH instruction to the normal XCH
instruction, it is necessary to set M8160 to OFF.
When using an instruction requiring the function extension flag in an interrupt program, program DI instruction (for
disabling interrupt) before driving the function extension flag, and program EI instruction (for enabling interrupt) after
turning OFF the function extension flag.
Error flag Error code storange device
Error detected step number storange device
FX3U/FX3UC PLC FX3G PLC
M8067 D8067 D8315, D8314, D8069 D8069
Error flag Error code storange device
Error detected step number storange device
FX3U/FX3UC PLC FX3G PLC
M8068 − D8315, D8314, D8068 D8068
X000
FNC 17
XCHP
D10 D11
X000
FNC 17
XCHP
D10 D10
Same number
M8160
M8160
Function extension flag
for the XCH instruction