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Agenda for Today• Overview of FPLDs
– History
– Tradeoffs
• CPLDs– General Description
– Basic Architecture
• Specific Vendor Devices– Xilinx
– Altera
• Xilinx XC9500 Series• CPLD Problems
1
Hierarchy of Logic Implementations
AcronymsSPLD = Simple Programmable Logic Device PAL = Programmable Array LogicCPLD = Complex PLDFPGA = Field Programmable Gate ArrayASIC = Application Specific IC
Common ResourcesConfigurable Logic Blocks (CLB)
– Memory Look-Up Table (LUT)– AND-OR planes– Simple gates
Input / Output Blocks (IOB)– Bidirectional, latches, inverters, pullup/pulldowns
Interconnect or Routing– Local, internal feedback, and global
Logic
StandardLogic
ASIC
ProgrammableLogic Devices
(FPLDs)
GateArrays
Cell-BasedICs
Full CustomICs
CPLDsSPLDs(e.g., PALs) FPGAs
today’s focustoday’s focus
2
Field-Programmable Logic Devices• Component function is defined by user under program
control• Logic Cells are interconnected by programming• Advantages:
– Flexible design that changes by reprogramming, ease of design changes
– Reduce prototype-product time– Large scale integration (over
100,000 gates)– Reliability increased, low financial
risk– Smaller device, low start-up cost
3
FPLD Capacities
• “Equivalent gates” refers loosely to the number of two-input NAND gates.
• The chart serves as a guide for selecting a device for an application according to the logic capacity needed.
• Each type of FPLD is inherently better suited for some applications than for others.
4
Digital Technology Tradeoffs
S
5
Which Implementation Technology?• Economic versus technical factors
– The next few slides off a comparison of economic and technical factors associated with these technologies
6
SPLDSSI/MSI
semicustom semicustom technologiestechnologies
standardstandardcomponentscomponents
CPLDFPGA
GateArray
Std.Cell
FullCustom
Comparison of Implementations• The table below offers a comparison of the major
implementation technologies over four key factors
7
SSI/MSI SPLD FPGA Gate ArrayStandard
CellFull
Custom
Gates/Component 5 - 100 50 - 5K 100 - 10K 500 - 100K 10K - 500K 100K - 10M
Cost/Gate High
Low
NRE Cost ($) - 1-2K 2-10K 5-50K 10-100K 50K-5M
Development time (weeks)
- 1-2 1-2 2-20 5-50 20-200
Comparison of Implementations
Circuit Cost As A Function Of Volume
Discrete
Full custom
Volume
Cost
8
Evolution of Implementations• CPLDs and FPGAs continue to evolve in parallel
9
1960
1970
1980
1990
2000
Today
SSI
MSI
LSI
VLSI
‘standard components’
‘semicustom components’
Gate Array
Standard CellsSimple PLD
CPLD FPGA
parallel development
Three FPLD Types• Simple Programmable Logic Device (SPLD)
– LSI device
– Less than 1000 logic gates
• Complex Programmable Logic Device (CPLD)– VLSI device
– Higher logic capacity than SPLDs
• Field Programmable Gate Array (FPGA)– VLSI device
– Higher logic capacity than CPLDs
10
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
Three FPLD Types• Simple Programmable Logic Device (SPLD)
– PLA or PAL
– Fixed internal routing, deterministic propagation delays
• Complex Programmable Logic Device (CPLD)– Multiple SPLDs onto a single chip
– Programmable interconnect
• Field Programmable Gate Array (FPGA)– An array of logic blocks
– Large number of gates, user selectable interconnection, delays depending on design and routing
– A high ratio of flip-flops to logic resources
11
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
SPLDs
• SPLDs = Simple PLDs• Popular SPLD Architecture Types
– Programmable Logic Array, PLA– Programmable Array Logic, PAL (Vantis)– General Array Logic, GAL (Lattice)– others
• Architecture Differences– AND versus OR implementation– Programmability (e.g., EE)– Fundamental logic block
12
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
SPLDs• We have already taken a close
look at SPLDs• A PLA-like SPLD is illustrated
at left– PAL and GAL devices offered
a somewhat better solution
• SPLDs are good alternative to using SSI and MSI devices– Especially if re-programmable
13
Logic Functions
Product Terms
Sums
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
SPLDs• Conventional programmable logic
– PALs, PLAs, GALs– standard parts like GAL22V10 and PAL16R4 are available from
multiple vendors
• Includes programmable logic cells to a limited degree (programming options in I/O cells, may have fixed AND/OR gates for logic), limited routing network
• Lowest density of all programmable devices, however, can offer very high performance
14
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
• SPLDs have nearly replaced TTL logic which was the dominate approach to logic implementation
15
How to Expand SPLD Architecture?• Increase number of inputs and outputs in a
conventional PLD?– e.g., 16V8 → 20V8 → 22V10
– Why not → 32V16 → 128V64 ?
• Problems: – n times the number of inputs and outputs requires n2 as
much chip area – too costly
– logic gets slower as number of inputs to AND array increases
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
16
How to Expand SPLD Architecture?• Solution:
– Multiple SPLDs with a relatively small programmable interconnect
– Less general than a single large PLD
– Can use software “fitter” to partition into smaller PLD blocks
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
CPLD Architecture
CPLDs• PALs and GALs are available only in small sizes
– equivalent to a few hundred logic gates
• For bigger logic circuits, complex PLDs or CPLDs can be used.
• CPLDs contain the equivalent of several PALs/GALs – linked by programmable interconnections– all in one integrated circuit (IC)
• CPLDs can replace thousands, or even hundreds of thousands, of individual logic gates – increased integration density
17
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
Complex PLDs• Some CPLDs are programmed using a PAL
programmer, but this method becomes inconvenient for devices with hundreds of pins.
• A second method of programming is to solder the device to its printed circuit board, then feed it with a serial data stream from a personal computer.
• The CPLD contains a circuit that decodes the data stream and configures the CPLD to perform its specified logic function.
18
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
Complex PLDs• Each manufacturer has a proprietary name for its
CPLD programming system • For example, Lattice calls it "in-system programming" • However, these proprietary systems are beginning to
give way to a standard from the Joint Test Action Group (JTAG)
19
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
• Xilinx, for example:• Xilinx CPLD devices that are cheaper and have fewer
gates than Xilinx FPGAs• Meant for interfacing rather than heavy computation• Built-in flash memory
– Compare to FPGA which needs external configuration memory
• Xess board has XC9572XL part– Approximately $2-$7 in quantities of one – vs. ~$15-20 for the Spartan2 FPGA on the board– Larger quantities much lower– 1600 gates, 72 registers
Complex PLDs versus FPGAs
20
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
21
CPLD Architecture• Simplified CPLD
architecture• Small number of largish
PLDs (e.g., “36V18”) on a single chip
• Programmable interconnect between PLDs
• Large number of I/O blocks
• Large number of pins
CPLD Architecture• Generalized
architecture for a complex PLD
• Programmable Interconnect Array – Capable of
connecting any LAB input or output to any other LAB
• Logic Array Blocks – Complex SPLD-like
structure
• Input/Output Blocks
22
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
CPLD Architecture• Each of the SPLD-like blocks in
a CPLD can be programmed as with a PAL or GAL
• Many SPLD-like blocks (e.g., LABs) are included in one CPLD
• LABs can be interconnected to build larger logic systems
23
CPLD Architecture
Feedback Outputs
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
CPLDs• Composition of Complex PLDs
– typically composed of 2-64 SPLDs
– interconnected using sophisticated logic
– includes macrocells (more about these later)
– includes input/output blocks
• Economical for designing large systems• Fast – switching speed
24
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
CPLDs
• Complex PLD's have arrays of PLD's on one chip, with an interconnection matrix connecting them.
• Timing performance can be more predictable than FPGAs because of simpler interconnect structure.
• Density is normally less than most FPGAs (although high end CPLDs will have about the same density as low-end FPGAs).
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
• Performance of CPLDs is usually better than FPGAs, but depends on vendor, number of cells in CPLD, and compared FPGA.
25
CPLDs• The block diagram at
right for the Cypress Semiconductor CPLD (Ultra37128) illustrates the general architecture of CPLDs
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
26
Cypress Ultra 37000 Family• In-system reprogrammable
CMOS CPLDs– JTAG interface for
reconfigurability– Design changes do not cause
pinout changes– Design changes do not cause
timing changes
• High density– 32 to 512 macrocells– 32 to 264 I/O pins– Five dedicated inputs including
four clock pins
27
Cypress Ultra 37000 Family• Characteristics of devices in the Ultra 37000 Family
28
CPLDs• Complex Programmable Logic Devices
– Contain from 10-1000 macrocells– Each macrocell is equivalent to around 20 gates– Support up to 200 I/O pins
• The key resource in a CPLD is the programmable interconnect– Tradeoff between space for macrocells and space for
interconnect– Careful design will limit the connections between
macrocells
29
ProgrammableLogic Devices
(FPLDs)
CPLDsSPLDs(e.g., PALs) FPGAs
CPLD Architecture• Complexity of CPLD is between FPGA and SPLD
30
LAB – Logic Array Block / uses PALsLAB – Logic Array Block / uses PALsPIA – Programmable Interconnect ArrayPIA – Programmable Interconnect Array
CPLD Architecture• Example Logic Array Block
31
PLA-like AND arrayPLA-like AND arrayLiteral inputs (e.g., a, b, c)Literal inputs (e.g., a, b, c)
Extra function (e.g., g,Extra function (e.g., g,h) i/ps for OR termh) i/ps for OR term
D-FFD-FF
2:1 Mux2:1 Mux
Programmable Interconnect Array• Consists of connectors that run throughout the CPLD
to connect the macrocells in each LAB• The PIA also connects the AND gate and other
elements of the macrocells
32
CPLD/FPGA Vendors• The main vendors
33
34
CPLD Families• Identical individual PLD blocks (Xilinx “FBs”) replicated
in different family members– Different number of PLD blocks
– Different number of I/O pins
Xilinx Xilinx XC9500 XC9500 CPLD CPLD SeriesSeries
Typical CPLD Packages• CPLDs are made using 2 to 64 SPLDs • Packages use 44-pins to over 200-pins (or more)
35
Typical CPLD Packages• QFP = Quad Flat Package – A QFP is an IC package with leads extending from each of
the four sides.
– It is used primarily for surface mounting, no socketing
• TQFP = Thin Quad Flat Package • PQFP = Plastic Quad Flat Package • VQFP = Very small Quad Flat Package
• PLCC = Plastic Leaded Chip Carrier – A package related to QFP
– Similar but has pins with larger distance, curved up underneath a thicker body to simplify socketing
36
CPLD Package Types• CSP = Chip Scale Package
– IC package with an area no greater than 1.2 times that of the die
• BGA = Ball Grid Array – A type of surface-mount packaging used for ICs
– Pins are replaced by balls of solder stuck to the bottom of the package
– The device is placed on a PCB that carries copper pads in a pattern that matches the solder balls
– The assembly is then heated causing the solder balls to melt
37
38
CPLD Families• Many CPLDs have fewer
I/O pins than macrocells– “Buried” Macrocells – provide
needed logic terms internally but these outputs are not connected externally
– IC package size dictates number of I/O pins but not the total number of macrocells
– Typical CPLD families have devices with differing resources in the same IC package
Xilinx CPLDs• Notice overlap in resource availability in a particular
package.
39
XC9572 CPLD Datasheet• XC9572 CPLD from Xilinx• 7.5 ns pin-to-pin logic
delays on all pins• 72 macrocells with 1,600
usable gates• Up to 72 user I/O pins• Four 36V18 Function
Blocks• Available in 44-pin PLCC,
84-pin PLCC, 100-pin PQFP and 100-pin TQFP packages
40
XC9572 CPLD Packages• XC9572 pinout for the 84-pin PLCC package and photo of
the 100-pin TQFP package
41
84-pin PLCC84-pin PLCC(pin 1)(pin 1)
100-pin TQFP100-pin TQFP
XC9572 CPLD Part Numbers• The part number for Xilinx CPLD devices includes
information as follows:
42
XC9500 CPLD Block Diagram• The XC9500 CPLD
family provides advanced in-system programming and test capabilities for high performance, general purpose logic integration.
• All devices are in-system programmable for a minimum of 10,000 program/erase cycles.
43
9500-Family Function Blocks (FBs)• 18 macrocells per FB• 36 inputs per FB (partitioning challenge, but also
reason for relatively compact size of FBs)• Macrocell outputs can go to I/O cells or back into
switch matrix to be routed to this or other FBs
44
9500-Series Macrocell• 18 macrocells per Function Block
45
Up to 5 product termsUp to 5 product terms
Programmable inversion Programmable inversion or XOR product termor XOR product term
Global clock or product-term clockGlobal clock or product-term clock
Set controlSet control
Reset controlReset control
OE controlOE control
9500-Series Product-Term Allocator• Share terms from above and below
46
programmableprogrammablesteeringsteeringelementselements
XC9500 Family
47
• An I/O block is composed of input buffer, output buffer, multiplexer for the output control and grounding control
• Slew rate control is used to smooth the rising and the falling edges of the output pulse.
• Grounding control is used to make the input/output pin (I/O) an earth ground (noise suppression).
• Each input/output pin can handle a 24-mA current.
9500-Series I/O Block• OE Multiplexer (OE
MUX) controls an output enable or stop.
• It is controlled by the signal from the macrocell or the signal from the GTS (Global Three-State control) pin.
• There are four GTS in XC95216 and XC95288 two in the others.
48
XC95108 CPLD Datasheet• XC95108 shares the
characteristics of all other XC9500 series devices
• 108 macrocells with 2400 usable gates
• Up to 108 user I/O pins• Six 36V18 Function Blocks• 10,000 program/erase
cycles• Available in 84-pin PLCC,
100-pin PQFP, 100-pin TQFP and 160-pin PQFP packages
49
XC95108 CPLD Datasheet• XC95108 block diagram
is similar to all of the others in the XC9500 family
50
Switch Matrix for XC95108• Could be anything from a limited set of multiplexers to
a full crossbar– Multiplexer -- small, fast, but difficult fitting
– Crossbar -- easy fitting but large and slow
51
52
Problems with CPLDs• Pin locking
– Small changes, and certainly large ones, can cause the fitter to pick a different allocation of I/O blocks and pinout
– Locking too early may make the resulting circuit slower or not fit at all
• Running out of resources– Design may “blow up” if it doesn’t all fit on a single
device
– On-chip interconnect resources are much richer than off-chip
– Larger devices are exponentially more expensive