FPGA Devices ECE 448 Lecture 5

ECE 448 Lecture 5 FPGA Devices ECE 448 – FPGA and ASIC Design with VHDL George Mason University Required reading • 7 Series FPGAs Configurable Logic Block: User Guide § Overview § Functional Details 2 What is an FPGA? Configurable Logic Blocks Block RAMs Block RAMs Block I/O Blocks Block RAMs ECE 448 – FPGA and ASIC Design with VHDL 3 Modern FPGA RAMRAM bblockslocks Multipliers/DSPMultipliers units LogicLog resourcesic blocks (#Logic resources, #Multipliers/DSP units, #RAM_blocks) Graphics based on The Design Warrior’s Guide to FPGAs Devices, Tools, and Flows. ISBN 0750676043 Copyright © 2004 Mentor Graphics Corp. (www.mentor.com) 4 Major FPGA Vendors SRAM-based FPGAs • Xilinx, Inc. ~ 51% of the market ~ 85% • Intel ~ 34% of the market (until 2015, Altera Corp.) • Lattice Semiconductor • Atmel (since 2016, subsidiary of Microchip Technology) • Achronix Semiconductor • Tabula (went out oF business in 2015) Flash & antifuse FPGAs • Microsemi SoC Products Group (until 2010 Actel) • Quick Logic Corp. ECE 448 – FPGA and ASIC Design with VHDL 5 Xilinx u Primary products: FPGAs and the associated CAD software Programmable CAD Software Logic Devices u Main headquarters in San Jose, CA u Fabless* Semiconductor and Software Company u TSMC (Taiwan) u UMC (Taiwan) {*Xilinx acquired an equity stake in UMC in 1996} u Seiko Epson (Japan) u Samsung (Korea) ECE 448 – FPGA and ASIC Design with VHDL 6 Xilinx FPGA Families Technology Low-cost Mid-range High-performance 220 nm Virtex 180 nm Spartan-II, Spartan-IIE 120/150 nm Virtex-II, Virtex-II Pro 90 nm Spartan-3 Virtex-4 65 nm Virtex-5 45 nm Spartan-6 40 nm Virtex-6 28 nm Artix-7 Kintex-7 Virtex-7 20 nm Kintex Virtex UltraSCALE UltraSCALE 16 nm Kintex Virtex UltraSCALE+ UltraSCALE+ FPGA Family 8 Artix-7 FPGA Family ECE 448 – FPGA and ASIC Design with VHDL 9 CLB Structure ECE 448 – FPGA and ASIC Design with VHDL George Mason University General structure of an FPGA Programmable interconnect Programmable logic blocks The Design Warriors Guide to FPGAs Devices, Tools, and Flows. ISBN 0750676043 Copyright © 2004 Mentor Graphics Corp. (www.Mentor.coM) ECE 448 – FPGA and ASIC Design with VHDL 11 Xilinx Artix-7 CLB ECE 448 – FPGA and ASIC Design with VHDL 12 Row & Column Relationship Between CLBs & Slices ECE 448 – FPGA and ASIC Design with VHDL 13 Chapter 2: Functional Details X-Ref Target - Figure 2-4 SRHI D COUT SRLO INIT1 Q Reset Type CE INIT0 CK SR Sync/Async FF/LAT DX DMUX D6:1 A6:A1 D O6 D O5 FF/LAT DX INIT1 Q DQ D INIT0 SRHI SRHI CE SRLO D SRLO CK Basic SR INIT1 Q CE INIT0 CK SR CX Components CMUX C6:1 A6:A1 C C O6 O5 FF/LAT CX INIT1 Q CQ of the Slice D INIT0 SRHI CE SRHI D SRLO SRLO CK INIT1 Q SR CE INIT0 CK SR BX BMUX LUTs B6:1 A6:A1 B B O6 FF/LAT O5 BX INIT1 Q BQ D INIT0 CE SRHI SRLO SRHI CK D SRLO SR INIT1 Q CE INIT0 CK SR AX AMUX Storage A6:1 A6:A1 A A O6 FF/LAT O5 AX INIT1 Q AQ Elements D INIT0 CE SRHI SRLO CK SR 0/1 SR CE CLK 14 CIN UG474_c2_03_101210 Figure 2-4: Diagram of SLICEL 20 www.xilinx.com 7Series FPGAs CLB User Guide UG474 (v1.7) November 17, 2014 Example of a 4-input LUT (Look-Up Table) (used in earlier families of FPGAs) • Look-Up tables x1 x 2 y x x x x y x3 LUT x x x x y are primary 1 2 3 4 x 1 2 3 4 0 0 0 0 1 4 0 0 0 0 0 0 0 0 1 1 0 0 0 1 1 elements for 0 0 1 0 1 0 0 1 0 0 0 0 1 1 1 0 0 1 1 0 logic 0 1 0 0 1 0 1 0 0 0 0 1 0 1 1 0 1 0 1 1 0 1 1 0 1 0 1 1 0 0 implementation 0 1 1 1 1 0 1 1 1 1 1 0 0 0 1 1 0 0 0 0 • Each LUT can 1 0 0 1 1 1 0 0 1 1 1 0 1 0 1 1 0 1 0 0 1 0 1 1 1 1 0 1 1 0 implement any 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 x x x x function of 1 1 1 0 0 1 2 3 4 1 1 1 0 0 1 1 1 1 0 1 1 1 1 0 4 inputs x1 x2 y y ECE 448 – FPGA and ASIC Design with VHDL 15 LUT of Artix-7 ECE 448 – FPGA and ASIC Design with VHDL 16 Chapter 2: Functional Details There are four additional storage elements that can only be configured as edge-triggered D-type flip-flops. The D input can be driven by the O5 output of the LUT or the BYPASS slice inputs via AX, BX, CX, or DX input. When the original four storage elements are configured as latches, these four additional storage elements cannot be used. Figure 2-5 shows both the register only and the register/latch configuration in a slice. X-Ref Target - Figure 2-5 DFF DFF/LATCH LUT D O5 Output LUT D Output FF INIT1 LATCH Q DQ INIT1 Q DQ D INIT0 D SRHIGH INIT0 DX CE SRLOW DX CE SRHIGH CK CK SRLOW SR SR CFF CFF/LATCH LUT C O5 Output LUT C Output FF INIT1 LATCH Q CQ INIT1 Q CQ D INIT0 D SRHIGH INIT0 CX CE SRLOW CX CE SRHIGH CK CK SRLOW SR SR Reset Type Reset Type SR SR Sync Sync LUT B O5 Output LUT B Output Async Async BFF BFF/LATCH FF INIT1 LATCH Q BQ Q BQ BX INIT0 BX INIT1 D SRHIGH D INIT0 CE CE SRLOW CE CE SRHIGH CK CK SRLOW CLK SR CLK SR AFF AFF/LATCH LUT A O5 Output LUT A Output FF INIT1 LATCH INIT0 Q AQ INIT1 Q AQ D SRHIGH D INIT0 AX CE SRLOW AX CE SRHIGH CK CK SRLOW SR SR 17 UG474_c2_04_101210 Figure 2-5: Two Versions of Configuration in a Slice: 4 Registers Only and 4 Register/Latch Control Signals The control signals clock (CLK), clock enable (CE), and set/reset (SR) are common to all storage elements in one slice. When one flip-flop in a slice has SR or CE enabled, the other flip-flops used in the slice also have SR or CE enabled by the common signal. Only the CLK signal has programmable polarity. Any inverter placed on the clock signal is automatically absorbed. The CE and SR signals are active-High. These initialization options are available for storage elements: •SRLOW: Synchronous or asynchronous Reset when CLB SR signal is asserted •SRHIGH: Synchronous or asynchronous Set when CLB SR signal is asserted 22 www.xilinx.com 7Series FPGAs CLB User Guide UG474 (v1.7) November 17, 2014 Reset and Set Configurations • No set or reset • Synchronous set • Synchronous reset • Asynchronous set (preset) • Asynchronous reset (clear) ECE 448 – FPGA and ASIC Design with VHDL 18 Two Different Types of Slices in Artix-7 ECE 448 – FPGA and ASIC Design with VHDL 19 Chapter 2: Functional Details X-Ref Target - Figure 2-4 SRHI D COUT SRLO INIT1 Q Reset Type CE INIT0 CK SR Sync/Async SLICEL FF/LAT DX DMUX D6:1 A6:A1 D O6 D O5 FF/LAT DX INIT1 Q DQ D INIT0 SRHI SRHI CE SRLO D SRLO CK INIT1 Q SR CE INIT0 CK SR CX CMUX C6:1 A6:A1 C C O6 O5 FF/LAT CX INIT1 Q CQ D INIT0 SRHI CE SRHI D SRLO SRLO CK INIT1 Q SR CE INIT0 CK SR BX BMUX B6:1 A6:A1 B B O6 FF/LAT O5 BX INIT1 Q BQ D INIT0 CE SRHI SRLO SRHI CK D SRLO SR INIT1 Q CE INIT0 CK SR AX AMUX A6:1 A6:A1 A A O6 FF/LAT O5 AX INIT1 Q AQ D INIT0 CE SRHI SRLO CK SR 0/1 SR CE CLK 20 CIN UG474_c2_03_101210 Figure 2-4: Diagram of SLICEL 20 www.xilinx.com 7Series FPGAs CLB User Guide UG474 (v1.7) November 17, 2014 Fast Carry Logic u Each SliceL and SliceM contains separate logic and routing for the fast generation MSB of sum & carry signals • Increases efficiency and performance of adders, subtractors, accumulators, comparators, and counters Routing Carry Logic Carry u Carry logic is independent of LSB normal logic and routing resources 21 Accessing Carry Logic u All major synthesis tools can infer carry logic for arithmetic functions • Addition (SUM <= A + B) • SuBtraction (DIFF <= A - B) • Comparators (if A < B then…) • Counters (count <= count +1) 22 Carry Logic Carry Logic In addition to function generators, dedicated fast lookahead carry logic is provided to perform fast arithmetic addition and subtraction in a slice. A 7 series FPGA CLB has two separate carry chains, as shown in Figure 1-1. The carry chains are cascadable to form wider add/subtract logic, as shown in Figure 2-2. The carry chain runs upward and has a height of four bits per slice. For each bit, there is a carry multiplexer (MUXCY) and a dedicated XOR gate for adding/subtracting the operands with a selected carry bits. The dedicated carry path and carry multiplexer (MUXCY) can also be used to cascade function generators for implementing wide logic functions.

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