Siemens SIMATIC S7-1200

Technology instructions
10.3 Motion control
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
711
10.3.6
Operation of motion control for S7-1200
10.3.6.1
CPU outputs used for motion control
The CPU provides four pulse output generators. Each pulse output generator provides one
pulse output and one direction output for controlling a stepper motor drive or a servo motor
drive with pulse interface. The pulse output provides the drive with the pulses required for
motor motion. The direction output controls the travel direction of the drive.
The PTO output generates a square wave output of variable frequency. Pulse generation is
controlled by configuration and execution information supplied through H/W configuration
and/or SFCs/SFBs.
Based upon the user’s selection while the CPU is in RUN mode, either the values stored in
the image register or the pulse generator outputs drive the digital outputs. In STOP mode,
the PTO generator does not control the outputs.
Onboard CPU outputs and outputs of a signal board can be used as pulse and direction
outputs. You select between onboard CPU outputs and outputs of the signal board during
device configuration under Pulse generators (PTO/PWM) on the "Properties" tab. Only PTO
(Pulse Train Output) applies to motion control.
The table below shows the default I/O assignments; however, the four pulse generators can
be configured to any digital output.
Note
Pulse-train outputs cannot be used by other instructions in the user program.
When you configure the outputs of the CPU or signal board as pulse generators (for use with
the PWM or motion con
trol instructions), the corresponding output addresses no longer
control the outputs. If your user program writes a value to an output used as a pulse
generator, the CPU does not write that value to the physical output.
Note
PTO direction outputs can be freed for use elsewhere in your program.
Each PTO requires the assignment of two outputs: one as a pulse output and one as a
direction output. You can use just the pulse output and not the direction output. You can then
free the direction output for othe
r purposes in your user program. The output cannot be used
for both the PTO direction output and in the user program, simultaneously.