Siemens SIMATIC S7-400H System Manual page 188

Using I/Os in S7–400H
13.4 Connecting redundant I/O to the PROFIBUS DP interface
Library V5.x Library V4.x Library V3.x Module
X
X
X
X
X
X
X
Central: Redundant DO dual-channel
X
X
188
X
DI16xDC 24 V
In some system states, it is possible that an incorrect value of the first module is
read in briefly when the front connector of the second module is removed. This is
prevented by using series diodes like those shown in figure F.1.
X DI32xDC 24 V
In some system states, it is possible that an incorrect value of the first module is
read in briefly when the front connector of the second module is removed. This is
prevented by using series diodes like those shown in figure F.2.
X DI 8xAC 120/230V
X DI 4xNamur [EEx ib]
You cannot use the module for applications in hazardous areas in redundant
mode.
Use with non-redundant encoder
You can only connect 2-wire NAMUR encoders or contact makers.

Equipotential bonding of the encoder circuit should always be at one point

only (preferably encoder negative).
When selecting encoders, compare their properties with the specified input

characteristics. Remember that this function must always be available,
regardless of whether you are using one or two inputs. Example of valid
values for NAMUR encoders: for "0" current > 0.2 mA; for "1" current > 4.2
mA.
X DI 16xNamur
Use with non-redundant encoder
Equipotential bonding of the encoder circuit should always be at one point

only (preferably encoder negative).
Operate the two redundant modules on a common load power supply.

When selecting encoders, compare their properties with the specified input

characteristics. Remember that this function must always be available,
regardless of whether you are using one or two inputs. Example of valid
values for NAMUR encoders: for "0" current > 0.7 mA; for "1" current > 4.2
mA.
X DI 24xDC 24 V
F module in standard mode
X DI 8xNAMUR [EEx ib]
F module in standard mode
X DO 32xDC 24V/0.5A
A clear evaluation of the diagnostics information "P short-circuit", "M short-
circuit" and wire break is not possible. Deselect these individually in your
configuration.
X DO 16xAC 120/230V/2A
Order number
6ES7 321–1BH02–0AA0
6ES7 321–1BL00–0AA0
6ES7 321–1FF01–0AA0
6ES7 321–7RD00–0AB0
6ES7321–7TH00–0AB0
6ES7326–1BK00–0AB0
6ES7326–1RF00–0AB0
6ES7422–7BL00–0AB0
6ES7422–1FH00–0AA0
System Manual, 03/2012, A5E00267695-11
S7-400H