Storing Plc Processing Program And Execution Mode; Path From Storage To Execution; Conversion Of Instruction Code At Execution; How To Confirm The Number Of Steps At Storage/Execution - Mitsubishi Electric M800VW Series Programming Manual

M800V/M80V Series PLC Programming Manual (1/2)
2 PLC Processing Program

2.8 Storing PLC Processing Program and Execution Mode

2.8 Storing PLC Processing Program and Execution Mode
The user PLC data area storage method and the PLC processing program execution method are explained. User PLC data
area is stored in the non-volatile ROM (hereinafter, built-in ROM) and a sequence program is executed according to the
following path.

2.8.1 Path from Storage to Execution

 During PLC development
Sequence program data transferred from development environment such as GX Developer/GX Works2 or built-in PLC (built-
in edit function) is stored in the volatile RAM (hereinafter, built-in RAM) for the temporary memory. The sequence program is
transferred to the PLC processor execution area before PLC execution, and is then executed.
The built-in RAM in the temporary memory is not held when the power is turned OFF. If the data needs to be held even after
the power is turned OFF, it must be stored in the built-in ROM.
There are following two ways to store the data to built-in ROM.
 Storing the sequence program of built-in RAM to the built-in ROM with PLC peripheral development environment (GX
Developer/GX Works2)
(Refer to "PLC Development Manual" for details.)
 Storing the sequence program of built-in RAM to the built-in ROM with built-in PLC (built-in edit function)
 At power ON
The data is transferred from the built-in ROM to the PLC processor execution area via the temporary memory built-in RAM,
and is then executed.
MELSEC instruction
Code format
Transfer
GX Developer

2.8.2 Conversion of Instruction Code at Execution

In the built-in ROM/temporary memory area shown on the left in the figure above, a sequence program is stored in the
instruction code format that is compatible with the MELSEC sequencer.
During execution, however, a sequence program is analyzed to optimize the references and/or converted into the PLC
processing processor instruction code for the CNC. Thus, the length (number of steps) of an instruction for each instruction
changes before and after the conversion. Refer to "6.1 Instruction List" for details on the number of steps during storage and
execution for each instruction.

2.8.3 How to Confirm the Number of Steps at Storage/Execution

The number of steps under the PLC development environment (GX Developer/GX Works2, built-in PLC (built-in edit function))
is usually all displayed as the number of steps at "storage".
The number of steps at execution can be checked with some dedicated methods. Refer to "PLC Development Manual" for
details.
IB-1501667-B
Built-in PLC (built-in edit
function)
Edit
Temporary
memory area Conversion
built-in RAM
Manual save At power ON
Built-in ROM
Right after the PLC RUN instruction,
converts into the PLC processor
instruction code method and copies
to the execution area.
PLC processor
execution area
CNC
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