Many 5volt chips will working with the output from a 3.3volt part. An example is the Arduino, it sees 3volts or more as a ‘1’. A 3.3volt device with 5volt tolerant pins, such as the Bus Pirate, can interact with an Arduino despite the voltage difference.
This table shows common logic threshold voltage levels and where they’re compatible. This is a big help for projects that need voltage translation.
The graph provides a comparison of Input and Output [I/O] logic switching levels for the CMOS, TTL, mixed CMOS/TTL, ETL, BTL, GTL, and Low voltage glue logic families. The graph above provides a comparison between the Input and Output [I/O] logic switching levels for CMOS, and TTL logic families.
The graph shows 5 volt CMOS, TTL, and mixed CMOS/TTL IC devices, and 3.3 volt LVTTL LVCMOS IC devices. BTL and GTL [Bus Driver] IC are shown for comparison. Note many Low Voltage [LV] CMOS families are 5 volt tolerant [not damaged by applying 5v to the input pins]. The output logic levels above are defined by the Terms section below. For a review of Noise Margin numbers and a short description of many of the IC logic families, refer to the Logic Family Selection page.