COP 3502 Introduction to Computer Science Memory Yashas

COP 3502: Introduction to Computer Science Memory Yashas Shankar

Overview of what you will learn today How a memory can store 0 and 1 A latch is used to store a current flowing inside itself Have current = 1 No current = 0 A latch is used to build a 1 -bit memory cell Store data (0 or 1) in to a latch Get data from a latch

Memory: A latch d q g q = data (0 or 1) g = select When g = 1, q = d When g = 0, q stays the same d = input data when g = 1

A latch d g q q = data (0 or 1) g = select When g = 1, q = d, when g = 0, q stays the same d = input data when g = 1

A latch: when g = 1, d = 1 d g q q = data (0 or 1) g = select When g = 1, q = d, when g = 0, q stays the same d = input data when g = 1

A latch: from previous slide when g goes back to zero (value of d will not effect q) d g q ** q stays at 1 ** q = data (0 or 1) g = select When g = 1, q = d, when g = 0, q stays the same d = input data when g = 1

A latch: when g = 1, d = 0 d g q q = data (0 or 1) g = select When g = 1, q = d, when g = 0, q stays the same d = input data when g = 1

A latch: from previous slide when g goes back to zero (value of d will not effect q) d g q ** q stays at 0 ** q = data (0 or 1) g = select When g = 1, q = d, when g = 0, q stays the same d = input data when g = 1

1 -bit memory cell Read/write data in/out d q g select Select = 0 nothing happens Select = 1 { read/write = 0 read, read/write = 1 write }

Example#1: (discuss in class) Read/write data in/out d q g select Select = 0 nothing happens Select = 1 { read/write = 0 read, read/write = 1 write }

Example#2: (discuss in class) Read/write data in/out d q g select Select = 0 nothing happens Select = 1 { read/write = 0 read, read/write = 1 write }

Example#3: (discuss in class) Read/write data in/out d q g select Select = 0 nothing happens Select = 1 { read/write = 0 read, read/write = 1 write }

4 -bit memory cell a 3 a 2 a 1 a 0 1 -bit Read/write select

16 -bit memory group Figure 7. 19 page 298 (also discuss in class)