Transcript Unit 4 PowerPoint Slides

EET 1131 Unit 4
Programmable Logic Devices
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Read Kleitz, Chapter 4.
Homework #4 and Lab #4 due next
week.
Quiz next week.
Programmable Logic
Programmable Logic Devices (PLDs) are chips with a large
number of gates that can be configured with software to
perform a specific logic function. Major types of PLDs are:
SPLD (Simple PLD): the earliest type of programmable logic, used
for smaller circuits with a limited number of gates.
CPLD (Complex PLD): contain multiple SPLD arrays and interconnection arrays on a single chip.
FPGA (Field Programmable Gate Array): a more flexible
arrangement than CPLDs, with much larger capacity.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Programmable Logic
Advantages of PLDs over fixed-function chips include:
 Reduced complexity of circuit boards
• Lower power requirements
• Less board space
• Simpler testing procedures
 Higher reliability
 Design flexibility
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Approximate Equivalent Densities
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The Lattice GAL22V10 (a popular
SPLD) is equivalent to about 500 logic
gates.
A typical Altera MAX7000 CPLD is
equivalent to about 2500 logic gates.
A typical Altera Cyclone FPGA is
equivalent to about 50,000 gates.
Major PLD Manufacturers
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Three big names in this field are
 Xilinx, with 51% of market share
 Altera, with 34%
 Lattice, with less than 10%
Market share numbers retrieved from Wikipedia on
9/10/2014.
Some Product Lines from Altera and
Xilinx
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Altera
 CPLDs: MAX
 FPGAs: Cyclone, Arria, Stratix
 Programming software: Quartus II
Xilinx:
 CPLDs: CoolRunner, XC9500
 FPGAs: Vertix, Spartan, Kintex, Artix
 Programming software: ISE
PALs and GALs
SPLDs contain arrays of gates. Two important kinds of
SPLD are PALs (Programmable Array Logic) and GALs
(Generic Array Logic). A typical array consists of a matrix of
conductors connected in rows and columns to AND gates.
PALs have a one-time
programmable (OTP)
array, in which fuses are
permanently blown,
creating the product
terms in an AND array.
A
A
B
B
X
Simplified AND-OR array
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PALs
PALs are programmed with a specialized programmer that
blows selected internal fuse links. After blowing the fuses,
the array represents the Boolean logic expression for the
desired circuit.
A
A
B
B
What expression is
represented by the array?
X
X = AB + AB
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GALs
The GAL (Generic Array Logic) is similar to a PAL but can
be reprogrammed. For this reason, they are useful for new
product development (prototyping) and for training purposes.
A
A
B
B
GALs were developed by
Lattice Semiconductor.
X
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PALs and GALs
PALs and GALs are often represented by simplified
diagrams in which a single line represents multiple gate
inputs. The logic shown is for the same circuit shown earlier.
Input buffer
A
A
B
B
Single line with slash
indicating multiple AND
gate inputs
Fuse blown
X
X
2
AB
AB + AB
Fuse intact
X
X 2
AB
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
GAL22V10
The GAL22V10 is a typical
SPLD. It has 12 dedicated
inputs pins and 10 pins that
can be used as inputs or
outputs.
Link to datasheet
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
CPLDs
A complex programmable logic device (CPLD) has multiple logic array
blocks (LABs), each roughly equivalent to an SPLD. LABs are
connected via a programmable interconnect array (PIA). Various
CPLDs have different structures for these elements.
The PIA is the interconnection
between the LABs.
I/O
Logic array
block (LAB)
Logic array
block (LAB)
SPLD
SPLD
I/O
PIA
I/O
I/O
Logic array
block (LAB)
Logic array
block (LAB)
SPLD
SPLD
Logic array
block (LAB)
Logic array
block (LAB)
SPLD
SPLD
I/O
I/O
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FPGAs compared to CPLDs
CPLDs
Based on
programmable AND
array and fixed OR
array.
FPGAs
Based on look-up table
(LUT), which is
basically a truth table.
(Results in higher
density.)
Both are programmed using the same software,
using either schematic entry or text entry.
Programmable Logic Software
All manufacturers of programmable logic provide software
to support their products. The process is illustrated in the
flowchart.
The first step is to enter
the logic design into
a computer. It is done
in one of two ways:
1) Schematic entry
2) Text entry using a
hardware description
language (HDL).
Design entry
Schematic
HDL
Synthesis
Timing
simulation
Functional
simulation
Implementation
Device
programming
(downloading)
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Programmable Logic Software
Design entry
Schematic
HDL
In schematic entry, the design is drawn on a computer screen by
placing components and connecting then with simulated wires. After
drawing the schematic, it can be reduced to a single block symbol:
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Programmable Logic Software
Design entry
Schematic
HDL
•In text entry, the design is entered via a hardware
description language (HDL).
•Learning an HDL takes longer than learning to do
schematic entry. But for complex designs it can provide a
more powerful and simpler way to enter designs.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Some Popular Hardware Description
Languages
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Open-standard HDLs
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VHDL (IEEE 1076)
Verilog (IEEE 1364)
Proprietary HDLs
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CUPL
ABEL (Advanced Boolean Expression
Language, now owned by Xilinx)
AHDL (Altera HDL)
A VHDL Sample
One way of writing VHDL programs is to use Boolean-type statements.
There are two parts to such a program: the entity and the architecture.
The entity portion describes the I/O. The architecture portion describes
the logic. Following is a short VHDL program showing the two parts.
entity Example is
port (B,C,D: in bit; X: out bit);
end entity Example;
architecture Behavior of Example is
begin
X <= (B or C) and D;
end architecture Behavior;
Floyd, Digital Fundamentals, 10th ed
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Simulation
Functional
simulation
After entering the circuit, the circuit is tested in a
simulation. You can test the circuit with waveforms to
verify the operation.
The following shows the functional test of a counter
using a waveform editor:
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Device Programming
Device
programming
(downloading)
The final step is to send the programming file from the
computer to the target device and test the implementation.
Shown is an Altera DE2-115 board with an Altera FPGA, along with
switches, LEDs and many other I/O devices for testing your design
after you’ve downloaded it to the FPGA.
© 2009 Pearson Education, Upper Saddle River, NJ 07458. All Rights Reserved
Our Software and Equipment
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Software: Altera’s Quartus II, version
13.0 sp1. (Free download, so you can
install it at home.)
Hardware:
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Altera Cyclone IV FPGA.
Chip is mounted on Altera’s DE2-115
experimenter’s board. (Manual on course
website.)
Three Ways of Representing a
Digital Circuit
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We have at least three ways of
describing a digital circuit:
1.
2.
3.
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Diagram showing the logic gates.
Boolean expression.
Truth table.
Given any one of these, you should
be able to write the other two.
See examples on following slides.
From Gate Diagram to Boolean
Expression or Truth Table
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Given a gate diagram, you should be able to:
1.
Write a Boolean expression for the diagram.
2.
Write the truth table for the diagram.
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Example: Write a Boolean expression and the
truth table for the following gate diagram.
A
B
C
X
From Boolean Expression to Gate
Diagram or Truth Table
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Given a Boolean expression, you should be able to:
1.
Draw a gate diagram that implements the
expression.
2.
Write the truth table for the expression.
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In many cases your job will be easier if you first use
Boolean algebra or a Karnaugh map to simplify
the expression. We’ll study these techniques next
week.
Example: Draw a gate diagram and write the truth
table for
X = AB + ABC
From Truth Table to Boolean
Expression or Gate Diagram
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1.
2.
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Given a truth table, you should be able to:
Write a Boolean expression for that truth
table. Here’s how:
a)
For each row in the truth table with a 1 in the
output column, list the corresponding AND term of
the input variables.
b)
OR together all of the AND terms from Step a.
Draw a gate diagram that implements the
truth table.
Example: Write a Boolean expression and
draw a gate diagram for the truth table on the
next slide.
Example: From Truth Table to Boolean
Expression or Gate Diagram
A
B
C
X
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