Configuring A Pulse Channel For Pwm - Siemens SIMATIC S7 System Manual

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101BExtended instructions

Table 8- 121 Default output assignments for the pulse generators

Signal board

Signal board

Signal board

Signal board

Configuring a pulse channel for PWM

To prepare for PWM operation, first configure a pulse channel in the device configuration by

selecting the CPU, then Pulse Generator (PTO/PWM), and choose either PWM1 or PWM2.

Enable the pulse generator (check box). If a pulse generator is enabled, a unique default

name is assigned to this particular pulse generator. You can change this name by editing it

in the "Name:" edit box, but it must be a unique name. Names of enabled pulse generators

will become tags in the "constant" tag table, and will be available for use as the PWM

parameter of the CTRL_PWM instruction.

The maximum pulse frequency of the pulse output generators for the digital output is

100 KHz (for the CPU), 20 KHz (for a SB), or 200 KHz (for a high-speed SB). However,

STEP 7 does not alert you when you configure an axis that with a maximum speed or

frequency that exceeds this hardware limitation. This could cause problems with your

application, so always ensure that you do not exceed the maximum pulse frequency of the

You have the option to rename the pulse generator, add a comment, and assign parameters

● Pulse generator used as follows: PWM or PTO (choose PWM)

● Output source: onboard CPU or SB

● Time base: milliseconds or microseconds

● Pulse width format:

– Hundredths (0 to 100)

– Thousandths (0 to 1000)

– Ten-thousandths (0 to 10000)

– S7 analog format (0 to 27648)

S7-1200 Programmable controller

System Manual, 11/2011, A5E02486680-05

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