What has changed in the Positioning Wizard for PTO/PWM in STEP 7
The STEP 7 Micro/WIN V4.0 Positioning Wizard
now also supports an improved pulse train function (linear
inclinations, delayed interrupts, manual mode) for CPUs as from
firmware version V2.0 in addition to the previous pulse trains
(PTO) and the previous pulse train modulation (PWM). Nothing has
changed in the Positioning Wizard for EM253 modules.
S7-200 CPUs with firmware V2.0 or higher have integrated linear
change of pulse output as extension to the PTO function. CPUs with
a firmware version lower than V2.0 do not support this function
You can check the firmware of your CPU via the
STEP 7 Micro/WIN menu command PLC > Information....
The PTO always produces a square wave from a variable frequency.
With the PTO function of the STEP 7 Micro/WIN Positioning Wizard
you can configure more profiles for similar process steps of step
motors (using the PTO function or the EM253 module). More detailed
information on the PTO function of the Positioning Wizard is
available in the STEP 7 Micro/WIN V4.0 Help.
The PWM always produces a changeable pulse-duty factor from a
Differences between the "old" PTO (in CPUs with firmware
versions lower than V2.0) and the new integrated PTO:
- What are the differences between the "old" and "new"
integrated PTO functions?
Based on the change of cycle time
in the "old" function, acceleration and delay were an exponential
curve. With the new Positioning Wizard and a CPU of firmware
version V2.0 and higher you obtain a linear change. Linear
acceleration and delays are usually required for low-cost step
- Can an "old" program be used in a CPU with firmware >=
V2.0 without having to change the program?
It is possible
to use the program for new CPUs too.
- Can an "new" program also be used in a CPU with firmware
No. The linear pulse output is not supported by
the older CPUs.
- How can I produce the "old" pulse output with the
Positioning Wizard of STEP 7 Micro/WIN V4.0?
produce the old pulse output just as before with the PLS
Subprogram blocks that must be integrated into the user program
are created by the Positioning Wizard for PTO and PWM.
Subprograms created by the Positioning Wizard for the
integrated linear PTO on the CPU (as from firmware V2.0)
- PTOx_ADV (jog):
Stops the actual
continuous movement profile and increases the number of pulses
specified in the profile defined by the Positioning Wizard. This
subprogram is created when you have specified at least one
continuous run at a fixed speed with the PTOx_ADV option
enabled in the Positioning Wizard.
- PTOx_CTRL (initialize and control PTO function):
Must be activated in each cycle (at input EN) and may only be run
once by a subprogram call in your program.
- PTOx_RUN (run PTO profile):
Runs a specific positioning profile. This subprogram is generated
by the Positioning Wizard for PTO configurations if one or more
positioning profiles have been defined.
- PTOx_MAN (PTO manual mode):
Commands the program-controlled pulse generation.
- PTOx_LDPOS (load position):
Loads a current position parameter into the PTO function. The PTO
wizard creates this subprogram when a fast counter is chosen to
count the pulses.
Subprogram created for PWM:
If you have selected the PWM mode in the STEP 7 Micro/WIN Wizard
V4.0, the PWMxRUN subprogram is created.
In order to be able to implement PWM the time base for the time
cycles must be defined in the Wizard.
cycle time: (2...65535 milliseconds/microseconds)
pulse duration: (2...65535 milliseconds/microseconds)
The subprogram created with STEP 7 Micro/WIN V4.0 is different
from the subprogram created with STEP 7 Micro/WIN V3.2.x.
Fig. 1: STEP 7 Micro/WIN V3.2.x and V4.0 blocks
The block created by the Positioning Wizard is called "PWM_OUTx"
with STEP 7 Micro/WIN V3.2.x and "PWM0_RUN" with STEP 7 Micro/WIN
V4.0. A parameter (Error) for error identification has been added
in the new block.