a dynamic random access memory comprising a matrix of memory cells accessed via word lines and bit lines also has clamp signal lines . the word lines terminate at switching elements , controlled by the clamp signal lines , through which the word lines are normally clamped to ground . in a memory access or refresh cycle , the selected word line is temporarily disconnected from ground by activating the corresponding clamp signal line . at the end of the cycle , the selected word line is again clamped to ground prior to precharging of the bit lines , in preparation for the next cycle . non - selected word lines remain clamped to ground at all times , which prevents noise and improves data retention . unnecessary current dissipation is avoided because switching elements are switched and word lines are unclamped only when necessary .