CPLDs
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This document discusses CPLDs (Complex Programmable Logic Devices), including their general architecture, reprogrammability, density, and common vendors and families. CPLDs contain programmable macrocells (equivalent to around 20 gates each) connected by a programmable interconnect and support up to 200 I/O pins. They are between FPGAs and SPLDs in complexity. The document describes CPLD architecture including logic array blocks (LABs) and programmable interconnect arrays (PIAs). It provides examples of Xilinx CPLD families, packages, and a datasheet for the XC9572 device.
CPLDs
- 1. CPLDs • The block diagram at right for the Cypress Semiconductor CPLD (Ultra37128) illustrates the general architecture of CPLDs Programmable Logic Devices (FPLDs) SPLDs CPLDs FPGAs (e.g., PALs) 1
- 2. 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 2
- 3. Cypress Ultra 37000 Family • Characteristics of devices in the Ultra 37000 Family 3
- 4. 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 Programmable Logic Devices (FPLDs) SPLDs CPLDs FPGAs (e.g., PALs) 4
- 5. CPLD Architecture • Complexity of CPLD is between FPGA and SPLD LAB – Logic Array Block / uses PALs PIA – Programmable Interconnect Array 5
- 6. CPLD Architecture • Example Logic Array Block Extra function (e.g., g, h) i/ps for OR term 2:1 Mux D-FF PLA-like AND array Literal inputs (e.g., a, b, c) 6
- 7. 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 7
- 8. CPLD/FPGA Vendors • The main vendors 8
- 9. 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 XC9500 CPLD Series 9
- 10. Typical CPLD Packages • CPLDs are made using 2 to 64 SPLDs • Packages use 44-pins to over 200-pins (or more) 10
- 11. 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 11
- 12. 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 12
- 13. 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 13
- 14. Xilinx CPLDs • Notice overlap in resource availability in a particular package. 14
- 15. 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 15
- 16. XC9572 CPLD Packages • XC9572 pinout for the 84-pin PLCC package and photo of the 100-pin TQFP package 84-pin PLCC 100-pin TQFP (pin 1) 16
- 17. XC9572 CPLD Part Numbers • The part number for Xilinx CPLD devices includes information as follows: 17
- 18. 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. 18
- 19. 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 19
- 20. 9500-Series Macrocell • 18 macrocells per Function Block Set control Programmable inversion or XOR product term Up to 5 product terms Global clock or product-term clock Reset control OE control 20
- 21. 9500-Series Product-Term Allocator • Share terms from above and below programmable steering elements 21
- 22. XC9500 Family • 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. 22
- 23. 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. 23
- 24. 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 24
- 25. XC95108 CPLD Datasheet • XC95108 block diagram is similar to all of the others in the XC9500 family 25
- 26. 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 26
- 27. 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 27