Read-Write Memory
Static Random-Access Memory (SRAM): Storage Array implemented using flip-flops. Very fast (ɯns), dense (~16Mbits), relativel expensive. To write, Chip-select (/CS) and Write Enable (/WE) must be low. To read, /CS and Output Enable (/OE) must be low and /WE must be high.
Dynamic Random-Access Memory (DRAM): Storage Array implemented using single transistor & a capacitor. Fast (ns), very dense (~64Mbits). Control signals are Row address strobe (/RAS), Column Address Strobe (/CAS) and Write-Enable (/WE).
DRAMs use a destructive-read cycle, so the data must be written back after it is read.