Siemens Simatic S7-400 - Manual (Page 347)

Analog Modules
5-131
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Block Diagram of the SM 431; AI 8 16 Bit
Backplane
bus
interface
Bus
S7-400
M0+
M0+
R0
M0–
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH0
A/D
converter
Internal
supply
Figure 5-41 Block Diagram of the SM 431; AI 8 x 16 Bit
Note
An external protective network is required in the signal leads in accordance with
IEC 61000-4-5 (150 V/14 mm MOV across each + and – input to chassis ground)