Q. Illustrate Internal Organisation of RAM?

The construction displayed in Figure below is made up of one JK flip-flop and 3 AND gates. The two inputs to system are one input bit and read/write signal. Input is fed in complemented form to AND gate 'a'. Read/write signal has a value of 1 if it is a read operation. So at the time of read operation AND gate 'c' has read/write input as 1. Because AND gate 'a' and 'b' have 0 read/write input and if chip is selected it implies that this cell is currently being selected then output would become equivalent to state of flip-flop. In other words data value stored in flip-flop has been read. In write operation only 'a' and 'b' gates get a read/write value of 1 and they clear or set JK flip-flop depending on data input value. If data input is 0, flip-flop will go to clear state and if data input is 1, flip-flop will go to set state. In effect input data is reflected in state of flip-flop. So we say that input data has been stored in flip-flop or binary cell.

Figure: Internal Organisation of a 32 × 4 RAM

A 32 × 4 RAM means this RAM has 32 words, 5 address lines (2⁵ = 32) and 4 bit data word size. Please note that we can signify a RAM using 2^A×D where A is number of address lines and D is number of Data lines. Figure above is extension of binary cell to an integrated 32 × 4 RAM circuit where a 5 × 32 bit decoder is used. 4 bit data inputs come through an input buffer and 4-bit data output is stored in output buffer.

 A chip select (C¯S¯) control signal is used as a memory enable input. When CS = 0 which is C¯S¯ = 1 it enables complete chip for read or write operation. An R/W signal can be used for read or write operation. The word which is selected will determine overall output.  Since all the above is a logic circuit of equal length which can be accessed in equal time so the word RAM.