Using I/Os in S7–400H   
13.4 Connecting redundant I/O to the PROFIBUS DP interface 
  S7-400H 
188  System Manual, 03/2012, A5E00267695-11 
Library V5.x  Library V4.x  Library V3.x  Module   Order number 
DI16xDC 24 V  6ES7 321–1BH02–0AA0 
X    X 
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. 
DI32xDC 24 V  6ES7 321–1BL00–0AA0 X    X 
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    X  DI 8xAC 120/230V  6ES7 321–1FF01–0AA0 
DI 4xNamur [EEx ib]  6ES7 321–7RD00–0AB0 X    X 
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. 
DI 16xNamur  6ES7321–7TH00–0AB0 X    X 
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. 
DI 24xDC 24 V  6ES7326–1BK00–0AB0 X    X 
F module in standard mode 
DI 8xNAMUR [EEx ib]  6ES7326–1RF00–0AB0 X    X 
F module in standard mode 
Central: Redundant DO dual-channel 
DO 32xDC 24V/0.5A  6ES7422–7BL00–0AB0 X    X 
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    X  DO 16xAC 120/230V/2A  6ES7422–1FH00–0AA0