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FX Series Programmable Controllers Devices in Detail 4
4-36
4.13.1 Modifying a Constant
Constants can be modified just as easily as data registers or bit devices. If, for example, the
constant K20 was actually written K20V the final result would equal:
K20 + the contents of V
Example:
4.13.2 Misuse of the Modifiers
Modifying Kn devices when Kn forms part of a device description such as KnY is not possible,
i.e. while the following use of modifiers is permitted;
K3Z
K1M10V
Y20Z
Statements of the form:
K4ZY30
are not acceptable.
• Modifiers cannot be used for parameters entered into any of the 20 basic instructions,
i.e. LD, AND, OR etc.
4.13.3 Using Multiple Index Registers
The use of multiple index registers is
sometimes necessary in larger programs or
programs which handle large quantities of
data. There is no problem from the PLC’s
point of view in using both V and Z registers
many times through out a program. The point
to be aware of is that it is sometimes
confusing for the user or a maintenance
person reading such programs, as it is not
always clear what the current value of V or Z
is.
Example:
V = 10 (K10)
Z = 20 (K20)
D5V = D15 (D5 + V = D5 + 10 = D15)
D15Z = D35 (D15 + Z = D15 + 20 = D35)
D40Z = D60 (D40 + Z = D40 + 20 = D60)
Both V and Z registers are initially set to K10 and K20 respectively.
The contents of D15 is added to that of D35 and store in D60.
V is then reset to 0 (zero) and both V and Z are used in the double word addition (DADD).
The contents of D1, D0 are then added to D3, D2 and then finally stored in D25, D24.
If V = 3276 then K20V ➭
K
20
V
(3276)
3296
X0
D40Z
X2
ADD D 5V
D 15Z
MOV K10 V
X1
MOV K20 Z
M8000
MOV K0 V
D 4Z
X3
DADD
D 0 D 2