[?]: How to count number of bits?

[Scarch]

The PLC is an L33ER.
I have 48 bits to be enabled/disabled from an operator panel.
I need to know how many of them are set to one.
Every bit means a machine, but they can be different.
For example, I set only the machines 1 to 8 to ON, so I have 8 machines enabled. But I can also set the machines 40, 2, 24, 35, 11, 12, 44 and 1 to ON, getting the same result (8 machines enabled).
I have no idea, please help.

Thanks a lot

[Schtiel]

May be File Bit Comparison (FBC) instruction will help. See this thread.