Siemens Sinumerik 828D Manual page 77

Connection notes
1. Recommended connection:
If both inputs and outputs are operated on a digital inputs/outputs group, it is recommended
that both the inputs and the outputs are fed with the same 24 VDC supply:
Figure 6-1
2. Not recommended connection:
If the inputs and outputs supplied separately with power, the input current can exceed the
permissible value of 15 mA according to EN61131-2. This may possibly cause the signal
source to be overloaded:
Figure 6-2
X242 pin assignment
Pin
1
2
3
4
5
6
7
8
9
10
PPU and components
Manual, 05/2015, 6FC5397-2DP40-3BA4
Inputs and outputs on the same supply
Inputs and outputs on different supplies
Signal name
Not connected
Not connected
IN1 DIN1
IN2 DIN2
IN3 DIN3
IN4 DIN4
M4 MEXT4
P3 P24EXT3
O1 DOUT1
O2 DOUT2
NC variable Meaning
$A_IN[1] Digital NC input 1
$A_IN[2] Digital NC input 2
$A_IN[3] Digital NC input 3
$A_IN[4] Digital NC input 4
Ground for pins 3...6
+24 V power supply
$A_OUT[1] Digital NC output 1
$A_OUT[2] Digital NC output 2
Interface description
6.5 Digital inputs/outputs
77