RAM8 Chip

1. RAM8 Chip

RAM8 is a memory chip that consists of 8 registers, each capable of holding a 16-bit value. It provides read/write access to one of these registers, based on a 3-bit address input. If load is 1, the value at in is stored in the selected register; otherwise, the stored value is retained..

2. Truth Table

address (3-bit)	in (16-bit)	load	out (16-bit)	Notes
000	0000000000000000	0	previous value @ 000	Holds old value at address 000
011	1111111111111111	1	1111111111111111	Updates register 011 with new input
011	0000000000000000	0	1111111111111111	Reads updated value at address 011
100	1010101010101010	1	1010101010101010	Updates register 100 with new input
100	0000000000000000	0	1010101010101010	Reads updated value at address 100

3. Implementation (Logisim)

Representation of the RAM8 in the logisim software

4. Implementation (HDL)

RAM8 is built using 8 Register chips and a multiplexer/demultiplexer setup to route inputs and outputs based on the address.

CHIP RAM8 {
    IN in[16], load, address[3];
    OUT out[16];

    PARTS:
    DMux8Way(in=load, sel=address, a=la, b=lb, c=lc, d=ld, e=le, f=lf, g=lg, h=lh);

    Register(in=in, load=la, out=ra);
    Register(in=in, load=lb, out=rb);
    Register(in=in, load=lc, out=rc);
    Register(in=in, load=ld, out=rd);
    Register(in=in, load=le, out=re);
    Register(in=in, load=lf, out=rf);
    Register(in=in, load=lg, out=rg);
    Register(in=in, load=lh, out=rh);

    Mux8Way16(a=ra, b=rb, c=rc, d=rd, e=re, f=rf, g=rg, h=rh, sel=address, out=out);
}