Mitsubishi Electronics FX3G User Manual

FX

3S

/FX

3G

/FX

3GC

/FX

3U

/FX

3UC

 Series

Programming Manual - Basic & Applied Instruction Edition

6 What to Understand before Programming

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.

• When an operation error has occurred, M8067 turns ON and D8067 stores the operation error code number. 
• In  the  FX

3U

/FX

3UC

 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

3S

/FX

3G

/FX

3GC

 PLCs, 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.

• When an operation error has occurred, M8068 turns ON.
• In the FX

3U

/FX

3UC

 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

3S

/FX

3G

/FX

3GC

 PLCs, 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).

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.

M8067

D8067

D8069

D8315, D8314

D8069

M8068

−

D8068

D8313, D8312

D8068

X000

FNC 17

XCHP

D10

D11

X000

FNC 17

XCHP

D10

D10

Same number

M8160

M8160

Function extension flag
for the XCH instruction