MicroLogix 1500 :- Input Latch Enable

[SirLightBulb]

I may be being think here, but could someone explain how the "Input Latch Enable" works. Not familar with this range.

The help says "Input Latch
When the Mask bit is set, the corresponding input bit has latching enabled." which is less than helpful.

WHen I have played with this setting, my online-monitoring does not seem to show change of state, but the software seems to operate.

I suppose what I want to know is
a) What does it mean
b) How do I unlatch?
c) Does this mean the input is held until I read.

Thanks for in advance.

 

[Mickey]

A little more detail from the manual. (see PDF below)
Also a link to the Instruction Set Manual.
http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001_-en-p.pdf