ECE 287 – Lecture 12

• Memory 1

Announcements

• Next Quiz on Wednesday• Exam II – Nov 15th

AREA

SPEED

POWER

PRICE $$$

Starter…

Draw a circuit for the following:

while (A+B > 10)A--;

Memory

What is memory in a non technical context?What are some key words about memory?What happens in our brain?

Basic Latch

R

S

!Q

Q

Gated SR Latch

R`

S` Q

R

S

Clk

D Latch

Q

D

Clk

D Latch

clk

QD

D Latch

clk

D

Q

0 1 2 3 5 6 7 8 9 104

What does Q look like assuming no delays through gates?

Critical Path

Assume 1ns delay through all gates. Where’s the critical path

aff

clk

b

ff

clkc

o

Frequency

How fast can the circuit be clocked at?

1s is related to 1Hz

Frequency = 1/time

How many things per second?

Value Symbol Name Hz Terms s second 1 1 Hz10−1 s ds decisecond 1010−2 s cs centisecond 10010−3 s ms millisecond 1000 1 KHz10−6 s µs microsecond 1000000 1 MHz10−9 s ns nanosecond 1000000000 1 GHz10−12 s ps picosecond 1000000000000 1 THz10−15 s fs femtosecond10−18 s as attosecond10−21 s zs zeptosecond10−24 s ys yoctosecond

Problem Set

1. What is the output of the following circuit for each clock assuming the flip-flops are initialized as follows: ff0 = 1, ff1 = 0, ff2 = 0, and ff3 = 0. Does the sequence ever end or repeat? What might this be good for? What’s the critical path?

ff0 ff1 ff2 ff3

clk