Is it possible to use a digital potentiometer as a digital rheostat?
The MAX5483 and MAX5484 appear to be, the MAX5481 does not appear to be:


Source: MAX5481 datasheet

It appears the MCP4151 can be used as a rheostat:


Source: MCP4131 Datahsheet

Note 1 reads as follows: 


  Floating either terminal (A or B) allows the device to be used as a
  Rheostat (variable resistor).