Digital Electronics
Principles & Applications
Seventh Edition
Roger L. Tokheim
Chapter 12
Digital Systems
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
INTRODUCTION
•
•
•
•
•
•
•
•
Elements of a System
Complexity of ICs
Digital Games
Digital Clock
Multiplexing Displays
Simplified Frequency Counter
Digital Timer
JTAG/Boundary Scan Technology
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Elements of a System
Control
Input
Storage
Processing
Storage
Output
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
A System- Classical Computer Organization
Control
Input
Memory
Output
Arithmetic
and Logic
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
Q#1Q#2In
classical
computer
organization,
the
block
Q#3-In
Inclassical
classicalcomputer
computerorganization,
organization,the
theblock
block
labeled
labeled
would
be
the
___
section.
labeledABCwould
wouldbe
bethe
the___
___section.
section.
ANS:
control
ANS:
memory
ANS:
ALU
A
Input
B
Output
C
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Complexity of ICs
•The complexity of integrated circuits suggests an evolution
in the design and manufacturing of ICs starting in the 1960s.
SSI- small-scale integration- up to 12 transistors- early 1960s
MSI- medium-scale integration- 12-99 transistors, late 1960s
LSI- large-scale integration- 100-9,999 transistors, mid 1970s
VLSI- very large-scale integration- over 10,000 transistors,
1980s and beyond
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Digital Dice Games
Roll Dice
Clock
Counter
Mod-6
Decoder/
Driver
Clock
Counter
Mod-6
Logic Block
+5V
Roll Dice
+5V
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Digital Roulette Game
Audio
Amplifier
Spin
Wheel
+5V input
Power-up
Initializing
Circuit
Voltage
Controlled
Oscillator
(VCO)
Ring Counter
(shift register)
Simulated
Roulette
Display
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Hours
Minutes
Seconds
Decoder/driver
Decoder/driver
Decoder/driver
1 ppm
1 pph
Mod 12 counter
Mod 60 counter
Mod 60 counter
1 Hz
DIGITAL CLOCK
60 Hz
1 pps
 60
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. A digital clock consists of many counters used
to divide frequency and to serve as a temporary
memory to hold the last count at the inputs of
the decoder/drivers. (True or False)
True
2. A digital clock uses many shift registers to
convert from the BCD output of the counters to
seven-segment code and to drive the displays.
(True or False)
False
3. The primary input to a digital clock is a(n)
________ (known, unknown) frequency which
is divided into seconds, minutes, and hours
using counters.
known
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Multiplexed Displays
a
8
b
BCD4
c
2 7-seg d
1 driver e
f
g
Digit drivers
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
A Basic Digital
Frequency Counter
Start/stop
fX
Counters/decoders/drivers
Start/stop
1 second
fX
11 cycles are counted (fX = 11 Hz)
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. In driving displays, to turn on and then
off one of several displays each for a
short time in turn at a high enough
frequency so they appear to be lit
continuously is called _______________
(function polling, multiplexing).
2. A circuit who counts the number of
pulses from an unknown frequency
source in a given time then stops,
decodes the accumulated count, and
displays the count in hertz is called a
_________ (decade counter, frequency
counter).
multiplexing
frequency counter
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Digital Timer
Clock
(time base)
Input
controls
Self-stopping
Down counter
Latch/Decoder
Driver
Magnitude
comparator
Alarm
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
Q#1In this
digital timer
circuit, the
block labeled
A is a(n) ___
Q#2Q#3- In
Inthis
thisdigital
digitaltimer
timercircuit,
circuit,the
theblock
blocklabeled
labeledBCisisa(n)
a(n)___
___
(self-stopping
down
counter,
serial-load
shift
register).
(latch/decoder/driver,
shiftopregister).
(magnitude comparator,
amp).
ANS:
self-stopping
down counter
ANS:
latch/decoder/driver
ANS:
magnitude
comparator
Clock
(time base)
Input
controls
A
B
C
Alarm
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
JTAG / Boundary Scan
•
JTAG:
• Provides simple test access to ICs and circuit boards
• Is extendible - custom test needs can be met
• Allows quick and easy test generation and application
• Is NOT limited by IC complexity nor board density
•
JTAG/Boundary Scan circuits can test:
• the internal logic of each IC
•
•
•
the interconnections (nets) between ICs
the logic of ICs that are NOT JTAG compliant
JTAG/Boundary Scan can be used to:
• test and debug circuit designs
• find faulty circuit boards in manufacturing
• Troubleshoot previously working JTAG circuits
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
An Example JTAG Test
1. Test data is shifted in at TDI
& latched in the input BSCs
IC
C
o
r
e
1011
TDI
TMS
TCK
TAP
Controller
2. The latched data is used as
input data to the chip logic
0100 3. Output from the chip logic is
captured in the output BSCs
TDO
4. The captured test data is
shifted out through TDO
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
QUIZ
1. Boundary scan testing of complex circuit boards is
commonly know by what four letters that represent
the name of the original group that worked on this
method.
JTAG
2. JTAG provides simple test access to ICs and circuit
boards. (True or False)
True
3. JTAG which is also called boundary scan is the
name for a security technique used to guard
government buildings and military bases. (True or
False)
False
4. JTAG compliant pc boards are soaked in a special
varnish to make them resistance to chemical
vapors, moisture and radiation. (True or False)
False
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
REVIEW
•
•
•
•
•
•
•
•
Elements of a System
Complexity of ICs
Digital Games
Digital Clock
Multiplexing Displays
Simplified Frequency Counter
Digital Timer
JTAG/Boundary Scan Technology
©2008 The McGraw-Hill Companies, Inc. All rights reserved.