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Installation manual
CNC 8060
CNC 8065
4.
PLC PROGRAMMING.
(REF: 1402)
Directing instructions.
Understanding how real and image values work.
The following example shows how the PLC acts when working with real or image values.
For the given PLC program and with the resources initialized to zero, it shows the status of
all the resources at the end of each scan or cycle.
With real values (REA), output O5 goes high (=1) at the end of the first cycle scan, whereas
it needs 4 cycle scans when using image values (IMA).
In the first cycle, ()=M1 sets the real value of M1=1, but its image value is ·0·. Only at the
end of this cycle scan will it be ·1·.
The system is faster when working with real values (REA); whereas with image values (IMA),
it is possible to analyze the same resource throughout the whole program with the same
value, regardless of its current value.
L
Label.
It is used to identify a program line. It may be defined in two ways:
• With L followed by up to 7 digits (L1 - L9999999).
• With L_ followed by 8 characters (L_GEAR).
If it is defined within a module (CY1, PRG or PE), it identifies a program line and allows making
references or jumps.
If it is defined outside the modules, for example at the end of the program after END, it
indicates the beginning of a subroutine. It is the same as the SUB directing instruction.
If a program has more than one label with the same name or number, the PLC program will
issue the corresponding error message when generating the executable program.
SUB
Subroutine definition.
It indicates the beginning of a subroutine. A subroutine is a portion of the program that may
be called upon by any executable instruction.
It is defined with SUB followed by a blank space and up to 24 characters. A subroutine must
always end with an END instruction.
They must be defined outside the modules (PRG, CY1, PE), for example at the end of the
program after the directing instruction END.
A subroutine can also start with the L instruction and end with the END instruction.
SUB A22
···
END
Scan 1
Scan 4
Scan 3
Scan 2
M1 M2 M3 O5 M1 M2 M3 O5
11111111
11111110
11111100
11111000
00000000
REA IMA
()=M1
M3 = O5
M2 = M3
M1 = M2
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