A number of students have burned out FPGAs. The following describes
the probable cause. This has not been confirmed by experiment. I
really don't want to perform this experiment. The FPGAs that have
been fried are the 10K70 (the right hand one). The 10K70 is surface
mounted and it is expensive to replace. In addition, the pc board is
often damaged in trying to replace the 10K70. We have a limited
number of pc boards!
Altera states that unused pins MUST be unconnected. This is not
possible for the pins connected to the AD bus (see below). In
particular, you must not have the switches driving the AD bus unless
the Flex devices are tristated for all of the AD bus pins that are
driven by the switches. Remove the jumper used to enable the
switches by grounding NUSW. If in doubt, read the handout the
describes the kit wiring.
If you can't find it then look for it on the web page.
All of these AD bus pins must be used as inputs, outputs, or specifically
tri-stated. In addition, all pins that are connected to a 50 pin
connector (see below) should be used as inputs, outputs, or
specifically tri-stated.
Unfortunately, there is no easy way to tristate unused pins. Altera
literature says that unused pins are grounded and MUST be unconnected.
Unused pins must be specifically listed in the top level entity and
specifically tri-stated. See the example files tristate.acf and
tristate.vhd in the directory /mit/6.111/altera/tristate.
Please use the 10K10 (on the left) until you are familiar with the
use and programming procedures. This device is in a socket and at
least we can replace it if you burn it out.