Digital Potentiometer, Control of

Using a digital potentiometer (e.g. MCP4131 100k) how do you detect when the wiper has reached the limit of its' 'travel'. I shall be supplying it with a clock signal from a 555 Timer and I want it to sweep up & down from limit-to-limit. (I shall be using it as part of a 555 PWM circuit so the output runs up and down a scale - think of it driving a motor which constantly speeds-up and slows-down).

Those pots use an SPI serial interface. How will you generate that?

The pot wiper location is determined by the value of digital word input, so you know it's at the limit when you put in the highest or lowest value for the pot position. For that you need some digital logic (gates) to detect those two word values and reverse the count direction at either of those values.

Thank you for that, it gives me a direction to go off in.
WeeDougie