email@example.com wrote: >> http://www.oho-elektronik.de/pics/UM_GODIL.pdf > ... > - The PDF says: "I/Os are not 5V tolerant". I see a lot of resistors to > handle this. But is it still capable of driving the C64 plus some > extras? If not, what is needed to make it capable? For example, will > 74HCT245's and 541's do? They are using a level shifter or resistors for this. The level shifter has both 5v and 3.3v supplies and is bidirectional. If configured for just resistors, the board only provides current limiting and any overvoltage will go through the FPGA's ESD diodes. This only works if your input voltage is less than Vcc + 0.5v. The output stage is usually simpler unless the FPGA has to source a lot of current. 3.3V levels are compatible with 5V levels for Voh and Vol. Designing mixed voltage circuits is tricky but can usually be done in a straightforward way. Just be sure you test carefully. I've fried several FPGAs using improper diode clamping approaches. -- Nate Message was sent through the cbm-hackers mailing listReceived on 2010-02-03 21:00:07
Archive generated by hypermail 2.2.0.