Download Programmable logic Systems

Programmable Logic Systems
EEE540
Lecture 1
Dr. Jim Harkin
Semester 1
2011-2012
Contents
• Learning Objectives
• Introduction/Rationale for Hardware Implementations
• Introduction to Programmable Logic
• PROMS\PLD\PALs devices
• CPLDs devices
• Additional Reading List
• Summary
Learning Objectives
(i) Understand the factors considered when realising
computations on hardware
(ii) Appreciate the principle difference between the various
hardware implementation mediums
(iii) Understand the different programming technologies used
in programmable logic systems
(iii) Be able to differentiate between PROMs/PLA/PALs
(iv) Be able to appreciate the architecture of CPLDs
Introduction/Rationale
• Hardware digital design addresses the realisation of
functionality in electronic hardware.
• By tradition engineers have used general-purpose processors
executing software programs to implement functionality in
hardware.
• This provides an easy method of realising functionality.
• By tradition - suffers from slow speed-performance.
• Customised hardware such as ASICs
provide functionality at increased
performance levels.
Why Implement in Hardware?
• What are the deciding factors for realising functionality in
hardware?
- software/processor verses custom hardware argument.
• Software executing on a hardware processor provides high
flexibility with low performance.
• Custom hardware provides high performance with low
flexibility.
- is it that simple?
• No there are more factors to be considered!!
Implementation considerations
• What should an engineer consider when selecting a
implementation medium?
- Power consumption limits.
Speed performance required.
- Device area\size limits.
- Flexibility\re-use required.
- Domain specific features required and end-target
application domain.
- Financial cost constraints (can depend on sales
volume).
Categorizing Implementation
Technologies
• Implementation technologies can be divided into several
categories with varied levels of flexibility in implementation,
design re-use and manufacturing cost.
• Each category provides devices with varied technology
traits, e.g. speed, low-power, flexibility etc.
• Trade-off for selection of devices varies between cost of
production (cost\volume ratio), design-performance
specification and level of design flexibility
Implementation Paths
Application Design
Flexible Hardware
Fixed Hardware
Standard
ASIC
Fixed hardware
Full-custom
Processors
Semi-custom
Gate Array
SSI/MSI
Standard Cell
Custom Asic
New
start
SoC\SiP
& IP
Performance\flexibility trade-off
Flash
FPGA
Static
Fuse/
anti
C/PLD
E(E)
PROM
DSP
Micros
Implementation Trade-offs
• Provides definite implementation paths for designers with
estimated costs and design-times.
• Particular devices can provide speed and low-power but
without post-fabrication design flexibility.
• ASICs (semi) provide flexibility and low power for designs,
but with larger financial costs and substantial design-times.
• Standard provide lower cost off the shelve computing
component and shorter design-times, but possibly providing
lower performance and higher power consumption.
• Financial cost plays a major role in deciding which path a
initial design implementation will follow.
Standard Device Technology
• Standard devices are typically off-the-shelve computing
components
• Provide low cost solutions
• Power consumption and performance vary between devices
• Devices re-programmed by software, i.e. limited flexibility
• Inherently sequential, limited parallelism exploited
• Short design time
• Several different device technologies available including:
Microprocessor
Microcontroller (Harvard, 8-bit to 64-bit )
DSPs, i.e. domain-specific processors (32-bit)
Full-custom Technology
• Full-custom designs can provide optimal implementations, i.e.
lowest power consumption, fastest execution speeds
• Expensive due to cost of mask designs and small volume for
production; @ 40nm mask costs can exceed ~£1.6M
Pounds1…32nm is approaching
• Designs cannot be altered after fabrication, i.e. no reprogrammability or design flexibility
• Design times can be substantial up to 18 months
• Designs re-spins are often required increasing design time
• Example ASIC chip application include digital TV and VoIP
[1] http://www.electronicsweekly.com/Articles/2008/06/18/43977/achieving-first-time-success-at-40-nm.htm
Semi-custom Technology
• Semi-custom designs provide sub-optimal implementations,
i.e. power consumption can be modest compared to fullcustom and execution speeds are lower
• Non-expensive compared to full-custom as cost of mask
design can be amortized over large volumes for production
• Designs can be altered after fabrication, i.e. re-programmed
• Design times can be less as standard cell and gate arrays are
pre-defined components that can be easily incorporated, 9-12
months
• The trade-off of performance to obtain increased flexibility
and lower costs has seen the creation of programmable logic
Programmable Logic
What is Programmable Logic (PL)?
• PL is a system for encapsulating your digital circuitry into a
programmable integrated circuit device.
• Definition: A logic element whose operation is not restricted
to any particular function. It may be programmed at different
points of the life cycle.
• Programming stages of the life cycle:
1) at the earliest, it is programmed by the semiconductor
vendor (standard cell, gate array),
2) by the designer prior to assembly or field deployment,
3) or by the user, in circuit.
Programmable Logic Devices
• There are three types of programmable logic devices available:
1) PLA/PALs
2) SPLD/CPLD {Simple(S) and Complex(C) PLDs}
3) FPGAs
• Some types are only capable of implementing small levels of
digital logic.
• Others, like FPGAs, can hold a complete microprocessorbased embedded systems.
• In addition to this difference in size, there is also much
variation in architectures.
Programmable Logic Devices –
programmable technologies
• Programmable logic devices are available using several
different programmable technologies:
fuse
anti-fuse
volatile
non-volatile
switch
Programmable Logic Devices programmable technologies
• Fuse - This is a two-terminal programmable element that is
normally a low resistive element and is programmed or "blown"
resulting in an open or high impedance.
• Anti-fuse - This is a two-terminal element that is normally a
high resistive element and is programmed to a low impedance.
• Volatile memory – (uses actual memory ) The memory
elements lose their contents when power is removed from the
device. SRAM-based devices are volatile and require another
device to store their configuration program.
Programmable Logic Devices programmable technologies
Logic 1
Programmed
antifuses
Logic 1
Fat
a
a
Pull-up resistors
Pull-up resistors
NOT
NOT
b
&
&
y = !a & b
b
AND
AND
Fbf
NOT
NOT
y = a & !b
Fuse links
Anti-fuse links
SRAM
Diagrams: Clive Maxwell – “The Design Warrior’s Guide to FPGAs”
Volatile memory – SRAM
programmable
Programmable Logic Devices programmable elements
Non-volatile memory - The memory elements keep their
contents when power is removed from the device, e.g. Flash,
EEPROM, EPROM
- The memory element may be one-time programmable or reprogrammable.
- Programmable devices can be both non-volatile and reprogrammable.
• Switch - This device consists of a memory element (either
volatile or non-volatile) which controls a switch. Volatile
SRAM-based memory elements are commonly used today.
Classifying Devices
• Device can be classed based on their level of programmability
- One Time Programmable: Devices can be programmed only
once; it's contents can not be changed. While typically these
devices are fuse or anti-fuse based, they can also be low-cost
EPROM devices.
- Re-programmable: These devices can have their
configuration loaded more than once. SRAM-based and Flashbased devices may be reloaded without restriction.
Implementation Paths
Application Design
Standard
ASIC
Full-custom
Processors
Semi-custom
Gate Array
SSI/MSI
Standard Cell
Custom
New
start
SoC\SiP
& IP
Flash
FPGA
Static
Fuse/
anti
C/PLD
E(E)
PROM
DSP
Micros
Programmable Logic Devices –
• Gate arrays
Transistors or gates are fabricated in a 2 dimensional array.
It forms the standard base of an application specific integrated
circuit (ASIC).
The device is programmed by custom metal layers interconnecting nodes in the array.
• Standard Cell
Pre-defined cells are used in an arbitrary structure.
This device differs from the gate array since each cell may be
different and optimized for each "standard" function.
PROM\PALs\PALs
PROMs\PLAS\PALs
What is the difference?
• PROM\PAL\PLAs are collectively know as SPLDs (simple
programmable logic devices)
Programmable Logic Devices PROMs
• Programmable read-only Memory (PROM) - The
programmable element for these devices include EPROM,
EEPROM, fuses and anti-fuses.
• PLAs have mostly replaced them.
a
b
&
w
x
l
Example Boolean function
c
Boolean circuit
y
a
b
c
w
x
y
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
1
0
1
0
1
1
0
Logic Table
Diagrams: Clive Maxwell – “The Design Warrior’s Guide to FPGAs”
Programmable Logic Devices PROMs
• Implementation
of Boolean
function on
PROM device
c
Predefined link
Programmable link
Address 0
&
Address 1
&
Address 2
&
Address 3
&
Address 4
&
Address 5
&
Address 6
&
Address 7
&
!a & !b & !c
!a & !b & c
!a & b & !c
!a & b & c
a & !b & !c
a & !b & c
a & b & !c
a & b & c
x
y
l
c
Predefined AND array
w = (a & b)
x = !(a & b)
y = (a & b) ^ c
Diagrams: Clive Maxwell – “The Design Warrior’s Guide to FPGAs”
l
w
l
&
l
a !a b !b c !c
a
b
b
Programmable OR array
a
w
x
y
Programmable Array Logic\
Logic Arrays
• PAL\PLAs have a simple structure comprising of a large
AND plane connecting to an OR plane with registered
outputs, i.e. Sum-of-products (SOP)
• First appeared in the late 1970s
• Logic designs are implemented by programming the
connections between device inputs, AND\OR planes and
device output pins
• Degree of connectivity is low (simple routing topology!)
• Devices are based on Fuse, EEPROM and Flash technology
• Fuse (one-time programmed), EEPROM and Flash (reprogrammable)
PAL\PLA
b
c
Predefined link
Programmable link
• General structure
&
• All links are
programmable
&
&
N/A
l
l
Predefined AND array
N/A
l
a !a b !b c !c
N/A
w
x
y
• Manufacturers include Cypress Logic, Philips, Atmel,
Lattice, AMD, Xilinx
• Example device, ispGAL 22V10A device from Lattice
Semiconductors
- 32-pin package (5mm x 5mm)
- 1.8 volt. supply with 100 micro amp standby
- 455 MHz clocking speed
- Less than $1 (volume > 50K)
Programmable
OR array
a
Courtesy Clive Maxwell
PAL\PLA
• Structure of Lattice ispGAL22V10A PAL
OR plane
Inputs
Inter-connections
Courtesy Lattice Data Sheet
AND plane
I\O with
F\Fs
PAL\PLA
• Provide low power consumptions but limited to the degree
of logic that can be implemented.
• Low power due to simple routing topology.
• Low capacitance from switching.
• Typically contain up to several thousand logic gates (Gate
count is a metric used to compare densities with ASICs).
• Generally used to implement simple glue logic, address
decoders, devices interfaces.
• Hardware designs for PAL\PLAs are generally written in
languages like ABEL or PALASM (hardware equivalents of
assembly).
PAL\PLA
• PAL Application
Sections of the system
implemented using PALs
Diagram: Xilinx Application Note
CPLDs
Complex Programmable Logic
Devices (CPLDs)
• CPLDs evolved from PAL\PLAs - as chip densities
increased, it was natural for the PLD manufacturers to evolve
their products into larger parts (several tens of thousands of
gates).
• Larger sizes of CPLDs allow either more logic equations or
more complicated designs to be realised.
• Current devices have additional logic and registers units and
more complex routing topologies than PAL/PLAs.
• Complex routing provides greater flexibility.
• Clock management, clock dividers + global routing lines.
CPLDs
• Sleep\standby power facilities available in modern devices.
• Core voltage supplies have dropped as low as 1.8v.
• Cheap solution for small and simple tasks, around £3-8.
• CPLD are also being used to interface between different
signalling levels, e.g. TTL to LVTTL.
CPLD Structure
• Generic structure - each of the four logic blocks are equivalent
to one PLD.
Programmable
Interconnect
matrix
2. SPLD
1. SPLD
3. SPLD
4. SPLD
Input/output pins
SPLD-like
blocks
• Each logic
block may also
be comprised of
macro cells and
interconnect
wiring, just like
an ordinary PLD.
Diagrams: Clive Maxwell – “The Design Warrior’s Guide to FPGAs”
• Manufacturers include Xilinx, Altera, Atmel, Actel, Lattice.
Example CPLD Device
• Example CPLD - Xilinx XC2C512 CoolRunner-II
- 180 Nanometer technology
- clocking speed 217MHz (Max 333MHz in family)
- core voltage 1.8v, (I/O requires 3.3v)
- Macro cell based structure (512 capacity)
- advanced routing with global clocks + clock dividers
- low power, typically several hundred micro amps
through DataGate feature
- Flash programming (20 yrs data retention)
- integrates with Xilinx FPGA software
- low cost solution, less than £5 (volume >10K)
CPLDs –Xilinx CoolRunner-II
• Family of devices and parameters
No. of I/O available
Clock speed
Courtesy Xilinx Data Sheet
No. of marco cells in device
CPLDs –Xilinx CoolRunner-II
• CoolRunner-II Architecture
PLAs
Macro Cells
I/O
Courtesy Xilinx Data Sheet
I/O
Advanced Interconnect
Matrix
CPLDs - Macro Cell (MC)
CoolRunner-II Macro Cell Structure
• Circuit functions are implemented by
configuring the muxes etc.
Feedback lines
Inputs
Outputs
Courtesy Xilinx Data Sheet
Additional
Logic
FF\Latch
CPLDs - Applications
CPLDs are still occasionally used for simple applications like
address decoding, but more often contain high-performance
control-logic or complex finite state machines.
Interface to micro-controller (FSM)
Interface to bus (change between voltage-standards)
Courtesy Xilinx Data Sheet
CPLDs - Applications
GPS Navigation Systems
- Hard disk controller
- GPIO interface
- Timing configuration
http://www.xilinx.com/products/silicon_solutions/cplds/coolrun
ner_series/coolrunner_ii_cplds/teardowns/gps.html
PDA
- LCD Timing Control
- GPIO Expansion
- Power Management
- Level Shifting
http://www.xilinx.com/products/silicon_solutions/cplds/c
oolrunner_series/coolrunner_ii_cplds/teardowns/pdas.ht
ml
CPLDs - Applications
GSM Phone
- Keypad scanner
- Logic consolidation
http://www.xilinx.com/products/silicon_solutions/cplds/coolrun
ner_series/coolrunner_ii_cplds/teardowns/gsm.html
Printer
- Controller and interface conversion
- Interface expansion
- Simple glue logic
http://www.xilinx.com/products/silicon_solutions/cplds/c
oolrunner_series/coolrunner_ii_cplds/teardowns/printer
s.html
CPLDs - Applications
P1200 portable handsets (Shenzhen Huayu Communications Technology Company, China )
• Altera MAX II CPLD
• Interfaces with:
- Radio Frequency Identification (RFID) reader
- Infrared Data (IRDA) sensor
- Bluetooth interface
http://connectiononline.blogspot.com/2008/06/huayu-communications-selects-alteras.html
CPLDs - Applications
Robot controller
CD/audio controller
http://www.youtube.com/watch?v=3Gi1x7m2RzI&mode=related&search
http://www.youtube.com/watch?v=Clix6szx16U
Summary
• Provided an introduction to hardware implementation
mediums.
• Introduced PLDs and the varied number of programmable
elements, PLD types and an example commercial device.
• Provided an overview of CPLDs and their advantages over
traditional PLDs.
• Presented a commercial CPLD device and highlighted its
features and applications.
Lecture Notes
Recommended reading – lecture notes
• Clive Maxwell – “The Design Warrior’s Guide to FPGAs”
Publisher Elsevier, 2005
Library shelf number: TK7872.L64.M28
Read pages 10- 41.