Specifications
SIMATIC Instructions
9-55
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
Assuming that the profile table is located in V memory starting at V500, the table
values used to generate the desired waveform are shown in Table 9-16.
Table 9-16 Profile Table Values
V Memory Address
Value
VB500 3 (total number of segments)
VW501 500 (initial cycle time - segment #1)
VW503 -2 (initial cycle time - segment #1)
VW505 200 (number of pulses - segment #1)
VW509 100 (initial cycle time - segment #2)
VW511 0 (delta cycle time - segment #2)
VW513 3400 (number of pulses - segment #2)
VW517 100 initial cycle time - segment #3)
VW519 1 (delta cycle time - segment #3)
VD521 400 (number of pulses - segment #3)
The values of this table can be placed in V memory by using instructions in your
program. An alternate method is to define the values of the profile in the data
block. An example containing the program instructions to use the multiple segment
PTO operation is shown in Figure 9-23.
The cycle time of the last pulse of a segment is not directly specified in the profile,
but instead must be calculated (except of course for the case in which the delta
cycle time is zero). Knowing the cycle time of a segment’s last pulse is useful to
determine if the transitions between waveform segments are acceptable. The
formula for calculating the cycle time of a segment’s last pulse is:
cycle time of last pulse=initial cycle time + (delta cycle time * (number of pulses - 1))
While the simplified example above is useful as an introduction, real applications
may require more complicated waveform profiles. Remember that:
The delta cycle time can be specified only as an integer number of
microseconds or milliseconds
The cycle time modification is performed on each pulse
The effect of these two items is that calculation of the delta cycle time value for a
given segment may require an iterative approach. Some flexibility in the value of
the ending cycle time or the number of pulses for a given segment may be
required.