Siemens S7-1200 System Manual page 936

Technical specifications
A.11 Digital signal boards (SBs)
Note
When switching frequencies above 20 kHz, it is important that the digital inputs receive a
square wave. Consider the following options to improve the signal quality to the inputs:
• Minimize the cable length
• Change a driver from a sink only driver to a sinking and sourcing driver
• Change to a higher quality cable
• Reduce the circuit/components from 24 V to 5 V
• Add an external load at the input
Table A- 187 Wiring diagrams for the 200 kHz digital input SBs
SB 1221 DI 4 x 24 VDC, 200 kHz
(6ES7 221-3BD30-0XB0)
①
Supports sourcing inputs only
Table A- 188 Connector pin locations for SB 1221 DI 4 x 24 VDC, 200 kHz (6ES7 221-3BD30-0XB0)
936
Pin X19
1 L+ / 24 VDC
2 M / 24 VDC
3 DI e.0
4 DI e.1
5 DI e.2
6 DI e.3
SB 1221 DI 4 x 5 VDC, 200 kHz
(6ES7 221-3AD30-0XB0)
System Manual, 03/2014, A5E02486680-AG
S7-1200 Programmable controller