Philip Balister wrote:
On page 18 of the Spartan-3E User Guide there is this paragraph:
Voltage Control
Consequently, these clock resources are also controlled by jumper JP9.
By default, JP9 is set
for 3.3V. The on-board oscillator is a 3.3V device and might not perform
as expected when
jumper JP9 is set for 2.5V
Can someone explain this to me? How much of a problem is this,
especially since we want to run bank 0 at 1.8 volts.
Yes - I read that prior to posting earlier. There are on-board 3.3V and
2.5V supplies and jumper J9 allows you to choose which one is active for
bank 0 I/O. The on-board 50MHz clock oscillator runs from this same
supply and isn't likely to handle lower voltages.
This shouldn't be a problem because there is an empty clock oscillator
socket available in which you could install an oscillator which would
run from 1.8V . Alternatively, the FPGA can accept clock inputs from
most any pin (although dedicated clock pins give the best input timing),
and you could put an oscillator on the interfacing board, or even use a
clock from the Beagle expansion connector.
Eric
