You will have to check the exact machine you are planning to use. And if its not what you are looking for another lab may have one. Generally I have seen only units that can do one or the other and not both.  But there may be very expensive single unit machines. 

If your reader is able to measure the absorbance at the required wavelength (according to the color of the product of your reaction) you can use the reader. You also need the volume of your assay to be compatible with the size of plate wells. If both requirements are fulfilled, you can use the machine...

For ELISA the plate is coated with antigen or antibody, other assays are done in solution. 

You can use your ELISA microplate reader for a variety of purposes that require optical density readings. The only thing you need to check beforehand is the wave length range that your machine is capable of reading. Also, a standard ELISA plate takes in 250 microliters per well maximum, so make sure you adjust the volume accordingly.

absorbance wavelength (machine capacity 400-800, assay requirement 405 : check)

and volume (ELISA vol 250 uL, assay requirement 50uL: check.

Thanks all