The RCM2200 User Manual (pg56) has ambiguous input voltage switching characteristics. Lists V(IL) at 0.7 x VDD (or 3.5v running at 5.0VCC), but V(T) at 2.4v. Which is it? 3.5V is difficult to achieve.
I don’t think it’s ambiguous. My reading of that table is:
- Rabbit 2000 guaranteed to read voltages < 0.3 x Vdd as low across the full voltage range.
- Rabbit 2000 guaranteed to read voltages > 0.7 x Vdd as high across the full voltage range.
- Rabbit 2000 typically switches between low and high with inputs at 2.4V (when Vdd is 5.0V at 25C).
My guess is that switch point could change with temperature.
If you want reliable operation but interface with 3.3V hardware, you might want to use level shifters. If you’re designing a new product, consider the RCM6700 or another module that operates at 3.3V.