Memory Elements and Arrays

Memory elements - used to store digital values for a future time.

General Memory Cell - 1 bit

• Input (write)

• M (hold)

• Output (read)

• Enable

Latches - basic element of memory cells

• storage achieved using bistable circuit (output is 0 or 1)

• "transparent" - output follows input sometimes

Set-Reset (SR) latch

• set - output is forced to 1

• reset- output is forced to 0

• NOR implementation

• Operations: hold, set, reset, unused

• NAND implementation

D Latch

• D input, Q output

Clocks and Synchronization

• period, T

• frequency, f

• n - nano, u - micro, M - mega

• clocked SR latch

• clocked D latch