Siemens SIMATIC FM 353 Manual page 272

Description of Functions
In all operating modes except Control mode, the "servo ready" signal is required for
the duration of every traversing movement when the parameter is active (MD37.2).
If the servo ready is not detected or is deactivated during the movement, the
"servo not ready" message is triggered (see Table 11-5, Class 3/No. 62).
Optional signal "Boost" / "PWM"
The interface signal "Boost" or "PWM" (pulse width modulation) permits optimized
operation of the stepper drive using phase current control. The FM 353 implements
these two functions via an output. This is done by alternate machine data selec-
tion.
The active level of the signal can be parameterized.
Signal response:
Idle
Acceleration/delay
Constant travel
The following table shows you the available machine data for parameterizing the
function.
MD
37 Special control signals
37.16 Boost active
37.17 Boost inverted
37.18 PWM active
37.19 PWM inverted
48 Boost duration absolute
49 Boost duration relative
50 Phase current travel
51 Phase current idle
Function, PWM:
The signal is generated as a 20 kHz frequency.
Boost function:
The signal is monitored with reference to the maximum absolute and relative active
phase.
9-72
Movement status
Designation
Output signal
"Boost"
inactive
active
inactive
Value/Meaning
0:Boost function not used
1:Boost function used
0:Boost signal high active
1:Boost signal low active
0:PWM function not used
1:PWM function used
0:PWM pulse high active
1:PWM pulse low active
1 − 1,000,000 ms
1 − 100%
Pulse duty factor [%]
FM 353 Stepper Drive Positioning Module
Output signal "PWM"
pulse duty factor per
MD 51
static active
pulse duty factor per
MD 50
Output signal
6ES7 353-1AH01-8BG0