Siemens SIMATIC S7-1200

Extended instructions
9.8 Pulse
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
487
9.8
Pulse
9.8.1
CTRL_PWM (Pulse width modulation)
Table 9- 185 CTRL_PWM (Pulse Width Modulation) instruction
LAD / FBD
SCL
Description
"CTRL_PWM_DB"(
PWM:=_uint_in_,
ENABLE:=_bool_in_,
BUSY=>_bool_out_,
STATUS=>_word_out_);
Provides a fixed cycle time output with a variable duty
cycle. The PWM output runs continuously after being
started at the specified frequency (cycle time). The
pulse width is varied as required to affect the desired
control.
1
When you insert the instruction, STEP 7 displays the "Call Options" dialog for creating the associated DB.
2
In the SCL example, "CTRL_PWM_DB" is the name of the instance DB.
Table 9- 186 Data types for the parameters
Parameter and type
Data type
Description
PWM IN HW_PWM
(Word)
PWM identifier: Names of enabled pulse generators will become tags in
the "constant" tag table, and will be available for use as the PWM pa-
rameter. (Default value: 0)
ENABLE IN Bool 1=start pulse generator
0 = stop pulse generator
BUSY OUT Bool Function busy (Default value: 0)
STATUS
OUT
Word
Execution condition code (Default value: 0)
The CTRL_PWM instruction stores the parameter information in the DB. The data block
parameters are not separately changed by the user, but are controlled by the CTRL_PWM
instruction.
Specify the enabled pulse generator to use, by using its tag name for the PWM parameter.
When the EN input is TRUE, the PWM_CTRL instruction starts or stops the identified PWM
based on the value at the ENABLE input. Pulse width is specified by the value in the
associated Q word output address.
Because the CPU processes the request when the CTRL_PWM instruction is executed,
parameter BUSY will always report FALSE. If an error is detected, then ENO is set to
FALSE, and parameter STATUS contains a condition code.
The pulse width will be set to the initial value configured in device configuration when the
CPU first enters RUN mode. You write values to the Q-word location specified in device
configuration ("Output addresses" / "Start address:") as needed to change the pulse width.
You use an instruction such as a move, convert, math, or PID box to write the desired pulse
width to the appropriate Q word. You must use the valid range for the Q-word value (percent,
thousandths, ten-thousandths, or S7 analog format).