Siemens SIMATIC S5 Manual page 271

Planning
When selecting the power unit, make sure that the maximum pulse frequency
processed without errors. To check that each power unit is ready for operation, there is a binary
input per axis,
Ready message (BB) from power unit
The IP247 requires 24 V active high at its input or a floating contact which can be supplied with
power by the IP247.
Voltage supply for a floating BB contact of the power unit (see above)
24 V/l 20 mA short-circuit proof
the power unit does not output a 24 V ready signal and does not have a floating contact, then
If
the 24 V output and the BB input must be jumpered at the cable end. The latter should be inside
the power unit to monitor that the cable is connected.
4
'
x5
X6
Fig. 7/2 Three possible ways of implementing the ready signal.
7 - 4
Pin 7
Pin 8
'
Pin 7
Pin 8
Pin 7
Pin 8
fmex can be
Floating
contact
I
Jumper
on/in
power unit