question re: Controllogix digital input modules

hi, I need to select digital input modules for a Controllogix PLC system for an industrial application. The inputs are various selector switches/pushbuttons and limit switch contacts. I'd like to use the 32 input card (1756-IA32) if possible but it notes that it is 32 "diagnostic inputs". what does that mean? how are these inputs different from the 1756-IA16 module?

thanks,

Welcome to the Forum!
"Diagnostic" I/O modules provide suplementary features such as Fault Time Stamp, No Load (Open Wire) detection, Test Pulse, etc.
Refer to Chapters 3 and 4 of :
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um058_-en-p.pdf