Introduction - If you have any usage issues, please Google them yourself
it can be for dsp ,it called serial and very useful for everybody read and study abouut dsp and so on,This feature is available only on the SST39VF800Q. This
pin functions as power supply pin for input/output buffers. It
should be tied to VDD(2.7-3.6V) in a 3.0V-only system. It
should be tied to a 5.0V±10 (4.5-5.5V) power supply in a
mixed voltage system environment where flash memory
has to be interfaced with 5V system chips. The VDDQpin is
not offered on the SST39VF800, instead it is a No Connect
pin.