Reference cell four-way switch for a simultaneous operation flash memory device

A flash memory system capable of simultaneous operation comprising:

• a read reference cell generating a read reference signal;
• one or more verify reference cells generating one or more corresponding verify reference signals;
• a mode select circuit generating selectively a read mode signal representing a read operation and a verify mode signal representing a verify operation, the mode select circuit further generating selectively an upper bank mode signal and a lower bank mode signal;
• a switch having a plurality of channel inputs, a control input, an upper channel output and a lower channel output;
• the switch being coupled at its channel inputs to the read reference cell and the one or more verify reference cells and coupled at its control input to the mode select circuit;
• the switch selectively generating at the upper channel output an upper read reference signal in response to the read mode signal, the upper bank mode signal and the read reference signal and an upper verify reference signal in response to the verify mode signal, the upper bank mode signal and the one or more verify reference signals;
• the switch selectively generating at its lower channel output a lower read reference signal in response to the read mode signal, the lower bank mode signal and the read reference signal and a lower verify reference signal in response to the verify mode signal, the lower bank mode signal and the one or more verify reference signals.