Hi dunnitagain,
do you have the 7535 IO termination board fitted? If not then the digital IOs of the DSPMC J4,J5,J11 and J12 are 3.3V capable and non isolated
per page 13 of the manual. The warning makes it pretty plain if you put 24V onto one of the inputs you'll blow it, in fact I would under no circumstances
put 5V on them either. 3.3V TTL is great stuff, fast as hell and really low power but don't do anything silly with it, its just not fault tolerant. Ask me how
I know and I will post you some ICs that I have VERY CUNNINGLY let the smoke out of!
No matter whether you use a proximity sensor or a hall sensor in absence of the 7535 board you must signal the input pin with 3.3V. I had a quick look
at the specs for an Omron prox sensor and it had a bandwidth of 500Hz, should be good for anything but a highspeed (>20,000rpm) spindle. However
the proximity sensor signalled full supply voltage, 10V min. So you would need some sort if interface which would include a 3.3V zener to prevent the
sensor from blowing the input pin.
The Honeywell hall sensor I linked has a power supply range of 2.7V to 7V, ie if you had a 3.3V supply or could derive one from a 5V output on the DSPMC
with a low dropout linear regulator then no interface is required, the signal from the hall sensor can be hooked directly to the input pin of the DSPMC.
If you do have the 7535 board then the prox sensor is pretty much plug and play.
Craig