
B-64044EN/01 SETTING 1.DeviceNet FUNCTIONS
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Ladder program processing and refreshing by the DeviceNet master function
Processing by the ladder program and refreshing by the DeviceNet
master function operate asynchronously with one another.
Processing by the ladder program can operate independently of
refreshing by the DeviceNet master function, so the ladder program
can be repeatedly executed at high-speed.
Fig. 3 shows a time chart of the internal operation of the CNC with
signals output from the ladder program.
Content of register A:
Content of register B:
0
0
1
1 2
2 3
3
mth
m+1
th
m+2
th
(nth)
1,1 2,2
3,3
Ladder program processing:
((n+1)th) ((n+2)th) ((n+3)th)
1 1 2 2 3
3
2,1
0
0
1
1 2
2 3
3
1, 1 2, 2
3,3
1 1 2 2 3 3
2, 1
Refresh processing of
DeviceNet master
function:
Transferred to slave
Fig. 1.3(c) Time chart
The upper part of the figure indicates that processing by the ladder
program is performed periodically and writing to register A or register
B is performed in the ladder program.
The middle part indicates that how register A and register B are
updated in this case. There are differences in the timing in which
data is written to register A or register B even in the same execution
cycle of the ladder program, so register A and register B are not
updated at the same time.
The lower part indicates that refreshing by the DeviceNet master
function is cyclically made to read data in register A and register B.
Since register A and register B are not updated at the same time, for
example, in the case of (n +1)-th refreshing, the data written by one
execution of the ladder program cannot be read as one set.
Conversely, when input signals from a slave are processed in the
ladder program, the data written by one execution of refreshing may
not be read by one execution of the ladder program.