Siemens SIMATIC S7-300 Manual page 256

Description of Functions
9.8.1 Function description of digital inputs
External start
The control signals of the axis include the start signal which triggers a posi-
tioning operation in "Reference point approach", "MDI" and "Automatic"
modes. A logical OR is established with the "External Start" digital input and
the control signal (ST).
External start is connected to digital input I1.
Example
ST
dig. "External start" input
Input I1 not inverted (MD36)
1
2
3
Minimum signal length at the digital input:
Enable input
The enable input signal must be set, if defined in MD34, for a positioning
operation/movement/output of the axis to take place. A reset stops the move-
ment (external movement enable).
Example
R+ or R–
Enable
1
2
3
9-80
1
2
In the Jogging and Control modes, the movement of the axis proceeds as
long as the AND link continues between the control signal (R+/R–) and
the enable input.
1
3
&
2
In the other modes, note the following:
If the enable input is still not enabled after a start edge, the start edge is
stored internally and "waiting for enable" is indicated by the checkback
signals. When the input is set, movement begins and the stored Start edge
is deleted (a Stop likewise deletes the stored Start edge).
3
1
Control signal (Start)
Input I1 inverted (MD36)
2 FM cycle
Positioning
FM 354 Servo Drive Positioning Module