Question

Instead of a single 32K RAM, your machine uses 4 small 8K RAMs. Demonstrate memory address decoding using:

(1) the 74HCT139 dual 2-to-4 line decoder,

and

(2) gates.

Notes: You will start with signals that are enough to turn ON the memory with:

(a) BUSRQST* or (b) A15 low, AND either:

(i) PSEN* (i.e. signal for reading program),

or

(ii) WR* or RD* (i.e. signals showing data transfer).

Answer 1