I should probably mention that using the 5V tolerant 3.3V device connected to that 5V TTL output will result in a zener of 3.6V (which is typically how the inputs are protected) to be conducting the entire time that the output level of the 5V device is above 3.6V. This means you will be burning power when the signal goes high. So if you plan on doing this make sure that the level which is predominately on the pin is a low level signal and not the 5V (high) output.