A read operation for a memory device. In response to an input address indicating to read data from a different page, a selected word line, first and second global bit lines and a selected first bit line group are precharged. A first cell current flowing through the selected word line, the first and the selected first bit line groups is generated. A first reference current flowing through the second global bit line group is generated. A first half page data is read based on the first cell current and the first reference current. The selected word line, the first and the second global bit lines are kept precharged. A second cell current flowing through the selected word line is generated. A second reference current is generated. A second half page data is read based on the second cell current and the second reference current.