Alberto:
You have taken a very stubborn hard line here in this thread. So much so that the crazy of it almost makes me roar with laughter.

You keep coming back to the question of Rigo with regards to the hard drive. The discussion of the voltage level capabilities of logic devices is directly suited to the issues that Rigo will have to deal with when he gets around to connecting up his hard drive. Most IDE type hard drives use 5V bus signals and some adaptations of them use lesser voltages. Interfacing such devices gets directly to the issue if the interface signals are suitable for connecting directly to motherboard ASIC or the prototype FPGA or the evaluation board microcontroller.

I can assure you that there are interfaces to 5V IDE devices on various motherboards, adapter boards and interface modules that most assuredly do not contain a single TTL chip from the SN74xxx family of parts that TI started making in the early 1970s. On the flip side I can also assure you that somewhere in the mismash of specs and data sheets of parts used to interface such devices that the term "TTL logic levels" or "TTL compatible" or "TTL voltages" is used.

Michael Karas