Installation manual
CNC 8035
7.
INTRODUCTION TO THE PLC
PLC program execution
(SOFT M: V15.3X)
(S
OFT T: V16.3X)
·288·
Therefore, the status of a resource may change during the execution of the PLC program.
Example, assuming that the initial status of resource M100 is "0":
M100 AND I7 = O3
Resource M100 = "0"
I10 = M100
M100 takes the value of resource I10
M100 AND I8 = M101
The value of M100 depends on the previous instruction.
This type of problems may be prevented by careful programming or by using "Image" resource
values (instead of "Real" values).
The PLC has 2 memories to store the status of the registers, the real memory and the image memory.
All the steps described so far work with the real memory. Saying "value of a particular resource"
is the same as saying "real value of a particular resource"
The image memory contains a copy of the values (status) that the resources had at the end of the
previous cycle. The PLC makes this copy at the end of the cycle. The resources having an image
value are: I1 thru I512, O1 thru O512 and M1 thru M2047
To Next Page
Loading...
