Siemens SIMATIC Manual page 64

Digital modules
3.6 Digital input module SM 321; DI 64 x DC 24 V, sinking/sourcing; (6ES7321-1BP00-0AA0)
Terminal assignment of SM 321; DI 64 x DC 24 V, Sinking/Sourcing
The figure below shows how channels are assigned to addresses (input byte x up to input
byte x+7).
40-pin terminal block
SM321; DI 64 X DC 24 V Sinking/Sourcing features two terminal blocks for connecting
actuators and sensors to the module front connector. A connecting cable is used to establish
the module connections.
64
S7-300 Module data
Manual, 06/2017, A5E00105505-AJ