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4 Understanding Programming
Caution
Program so that the memory area of the start address is not exceeded when using a
word address or symbol for the offset.
If an indirect specification causes the address to exceed the area of the start address,
the system will access data in other area, and unexpected operation may occur.
4-5-2
Application Examples for Address Offsets
It is possible to dynamically specify the offset by specifying a word address in I/O memory for the offset
in the brackets. The contents of the specified word address will be used as the offset.
For example, execution can be performed by increasing the address by incrementing the value in the
brackets and using only one instruction.
4
Ladder Program Example
The contents of corresponding words are added starting from the specified starting point, W0, to the
end of the areas and the sums are output to D200 to D299 starting from the specified offset from
D200.
For example, if W0 is 30, the corresponding words from D30 to D99 and D130 to D199 are added,
and the sums are output to D230 to D299.
Set the value of W0 to the offset word (W1) using the MOV instruction.
Use
the operand of the addition instruction to specify and execute D0[W1] +
D100[W1] = D200[W1].
Increment W1 to increase the offset.
Repeat this process
100 times.
Each process is performed with an input comparison instruction (<) as the execution condition so
that W1 does not exceed &100 to make sure that the upper limit of the indirect addressing range is
not exceeded.
Execution condition
a
<
W1
&100
MOV
W0
W1
When execution condition a (upwardly
differentiated) turns ON, the value of W0 is
set to W1.
FOR
&100
Starts FOR loop
+
D0[W1]
D100[W1]
D200[W1]
If execution condition a is ON and the
value of W1 is less than &100, the data
from the start position until D99 and
the data until D199 are added, and the
sum for each is output until D299.
++
While execution condition a is ON, W0 is
incremented.
W1
NEXT
CP1E CPU Unit Software User’s Manual(W480)
Returns to FOR
4-21
4-5-2 Application Examples for Address Offsets
In this example, two areas of consecutive data are used: D0 to D99 and D100 to D199.
Execution condition
a
4-5 Specifying Offsets for Addresses
For example, write the program so that processing is executed only when the indirect
specification does not cause the final address to exceed the memory area by using
an input comparison instruction or other instruction.