Read Only Memory ROM A block diagram of

Read Only Memory (ROM) • A block diagram of a ROM consisting of k inputs and n outputs is shown below. Number of words Size of word The inputs provide the address for memory, and the outputs give the data bits of the stored word that is selected by the address. The number of words in a ROM is determined from the fact that k address k input lines are needed to specify 2 words.

Read Only Memory (ROM) Draw a 32 8 ROM. The unit consists of 32 words of 8 bits each.

Read Only Memory (ROM)

Read Only Memory (ROM) Inputs outputs . I 4 I 3 I 2 I 1 I 0 A 7 A 6 A 5 A 4 A 3 A 2 A 1 A 0 0 0 1 0 1 1 0

Read Only Memory (ROM) Example 7. 1: Design a combinational circuit using a ROM. The circuit accepts a threebit number and outputs a binary number equal to the square of the input number. (minimize the ROM if possible)

Read Only Memory (ROM) Example 7. 1: Design a combinational circuit using a ROM. The circuit accepts a threebit number and outputs a binary number equal to the square of the input number. We need a ROM with a size = 8 4

Read Only Memory (ROM)

Programmable Logic Devices

Programmable Logic Array (PLA) F 1=AB+AC+ABC F 2=(AC+BC)

Programmable Logic Array (PLA) Example 7. 2 : Implement the following two Boolean functions with a PLA: F 1(A, B, C) = (0, 1, 2, 4) F 2(A, B, C) = (0, 5, 6, 7) F 1 F 2 F 1= AB+AC+BC F 2= AB+AC+ABC F 1= (AB+AC+BC) F 2= (AB+AC+ABC)

Programmable Logic Array F 1= (AB+AC+BC) F 2= AB+AC+ABC AB AC BC A B C

16 14

2^15

A) Without minimizing B) With minimizing

A) Without minimizing

B) With minimizing