data input/output [DQ(n)(x)]

The pins that serve as data output(s) when in the read mode and as data input(s) when in the write mode. When the device is not selected or enabled, the output(s) are in a floating state. On devices having both serial and parallel access ports, these pins provide access to the parallel RAM port data channels. The suffix (n) is a numeric value indicating the number assignment of a particular pin with numbering starting at 0. In some situations the letter "U" or "L" is used to indicate that the pins are assigned to the upper or lower byte of a two-byte data interface. In devices where the standard supports an optional 9th bit that may be used as a parity bit, the suffix P may be used in lieu of a numeric value. In devices where data bit groupings have independent control, an additional suffix "x" is applied. "x" takes the values of a, b, c, etc.

References: 

JESD21-C, 1/97