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7 Series DSP Resources Part 1

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Objectives After completing this module, you will be able to: Describe the primary usage models of DSP slices Describe the DSP slice in the 7 series FPGAs

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DSP Overview 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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* Source: Jan Rabaey, BWRC DSP/GPP * Traditional Processor Architectures SD/HD Video Radar Imaging 3G 4G SDR Performance (Algorithmic & Processor Forecast) Algorithm Complexity Need a solution to fill the gap Performance requirements are outpacing traditional DSP solutions Performance requirements are outpacing traditional DSP solutions LTE Growing DSP Performance Gap

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Typical DSP Operation Diagram of a typical FIR filter –Parallel computing process by nature –N number of taps –N multiplications should happen in parallel i=N-1 i=0 k i.X (n-i) Y (n ) = Viewed as an EquationViewed as a Diagram Multiply Accumulate N times Z -1 k0k0 k1k1 k2k2 k3k3 k N-1 X (n) Y (n) Multiply Delay (Register) Summation Coefficients Coefficient

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Sequential vs. Parallel DSP Processing Data Out Single-MAC Unit Coefficients 1.2 GHz 3960 clock cycles = 303 KSPS 3960 clock cycles needed Data In X + Reg 600 MHz 1 clock cycle = 600 MSPS Data Out FPGA - Fully Parallel Implementation (7 Series FPGA) 3960 operations in 1 clock cycle Data In X + C0 C0 X C1 X C2 X C3 X C2015 … Reg Reg Reg Reg Standard DSP Processor – Sequential (Generic DSP)

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DSP Slice Features Z -1 MULT Z -1 ADD Z -1 Z OpMode 7 48 A:B Y 36 X 0 17-bit shift A CE M REG DQ CE P REG DQ B 48 D ALUMode CarryIn 48 Z CE C REG DQ 1 4 = C or MC CE A REG DQ 2-Deep CE B REG D 2-Deep Q P PATTERN DETECT C Input Conditioning OP CTL

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FIR Filter Mapped to DSP Slices Coefficients are from left to right, causing the latency to be as large and grow with the increase of coefficients The input time delay series is created inside the DSP slice for maximum performance irrespective of the number of coefficients Dedicated cascade connections (PCOUT and PCIN) are exploited to achieve maximum performance This filter structure, while referred to as a Systolic FIR filter, is really a Direct Form Type I with one extra stage of pipelining K0K1 K2K3 0 DSP48E1 Slice opmode = DSP48E1 Slice opmode = x(n) y(n) 38 18

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Non-DSP Functions (Addition) START: This is the typical adder tree found in many signal processing designs Remove all pipelining from the tree. This makes it easier to understand and visualize the changes Rearrange the tree. Notice that functionally has not changed. The diagram has just been redrawn Pipelining is required for performance. Adding one in the chain requires one in the data path delay as well. Determining mapping to DSP48E is easy now

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DSP Review 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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Summary All 7 series FPGAs contain the same DSP48E1 cell –The DSP48E1 is identical to the one used in the Virtex-6 FPGA The DSP48E1 cell has the following features –25x18 signed multiplier –48-bit add/subtract/accumulate –Pipeline registers for high speed –Pattern detector –SIMD operators –Cascade paths –25 bit pre-adder –Dynamic pipeline control

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Where Can I Learn More? 7 Series DSP48E1 Slice User Guide –Slice description –Design consideration How to design to optimize for power and performance How to use advanced design techniques –Design recommendations for XST This guide has example inferences of many architectural resources –XST User Guide Refer to the Coding Techniques chapter Xilinx Education Services courses –www.xilinx.com/training Xilinx tools and architecture courses and other Free videos!

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Trademark Information Xilinx is disclosing this Document and Intellectual Property (hereinafter “the Design”) to you for use in the development of designs to operate on, or interface with Xilinx FPGAs. Except as stated herein, none of the Design may be copied, reproduced, distributed, republished, downloaded, displayed, posted, or transmitted in any form or by any means including, but not limited to, electronic, mechanical, photocopying, recording, or otherwise, without the prior written consent of Xilinx. Any unauthorized use of the Design may violate copyright laws, trademark laws, the laws of privacy and publicity, and communications regulations and statutes. Xilinx does not assume any liability arising out of the application or use of the Design; nor does Xilinx convey any license under its patents, copyrights, or any rights of others. You are responsible for obtaining any rights you may require for your use or implementation of the Design. Xilinx reserves the right to make changes, at any time, to the Design as deemed desirable in the sole discretion of Xilinx. Xilinx assumes no obligation to correct any errors contained herein or to advise you of any correction if such be made. Xilinx will not assume any liability for the accuracy or correctness of any engineering or technical support or assistance provided to you in connection with the Design. THE DESIGN IS PROVIDED “AS IS" WITH ALL FAULTS, AND THE ENTIRE RISK AS TO ITS FUNCTION AND IMPLEMENTATION IS WITH YOU. YOU ACKNOWLEDGE AND AGREE THAT YOU HAVE NOT RELIED ON ANY ORAL OR WRITTEN INFORMATION OR ADVICE, WHETHER GIVEN BY XILINX, OR ITS AGENTS OR EMPLOYEES. XILINX MAKES NO OTHER WARRANTIES, WHETHER EXPRESS, IMPLIED, OR STATUTORY, REGARDING THE DESIGN, INCLUDING ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND NONINFRINGEMENT OF THIRD-PARTY RIGHTS. IN NO EVENT WILL XILINX BE LIABLE FOR ANY CONSEQUENTIAL, INDIRECT, EXEMPLARY, SPECIAL, OR INCIDENTAL DAMAGES, INCLUDING ANY LOST DATA AND LOST PROFITS, ARISING FROM OR RELATING TO YOUR USE OF THE DESIGN, EVEN IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE TOTAL CUMULATIVE LIABILITY OF XILINX IN CONNECTION WITH YOUR USE OF THE DESIGN, WHETHER IN CONTRACT OR TORT OR OTHERWISE, WILL IN NO EVENT EXCEED THE AMOUNT OF FEES PAID BY YOU TO XILINX HEREUNDER FOR USE OF THE DESIGN. YOU ACKNOWLEDGE THAT THE FEES, IF ANY, REFLECT THE ALLOCATION OF RISK SET FORTH IN THIS AGREEMENT AND THAT XILINX WOULD NOT MAKE AVAILABLE THE DESIGN TO YOU WITHOUT THESE LIMITATIONS OF LIABILITY. The Design is not designed or intended for use in the development of on-line control equipment in hazardous environments requiring fail-safe controls, such as in the operation of nuclear facilities, aircraft navigation or communications systems, air traffic control, life support, or weapons systems (“High-Risk Applications”). Xilinx specifically disclaims any express or implied warranties of fitness for such High-Risk Applications. You represent that use of the Design in such High-Risk Applications is fully at your risk. © 2012 Xilinx, Inc. All rights reserved. XILINX, the Xilinx logo, and other designated brands included herein are trademarks of Xilinx, Inc. All other trademarks are the property of their respective owners.

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7 Series DSP Resources Part 2

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Objectives After completing this module, you will be able to: Describe the DSP slice in the 7 series FPGAs

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DSP Overview 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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7 Series DSP48E1 Slice PCIN A:B X MC 25 X 18 = P Y Z >> C P C’ 48 OpMode 7 CarryIn ALUMode 4 P CarryInSel 3 PCOUT INMODE P PATTERN_ DETECT ACINBCIN A B D CARRY CASCOUT CARRY OUT ACOUTBCOUT CARRY CASCIN MULT SIGNOUT 6 MULT SIGNIN 25 PATTERN Dual B Register Carry 5 Dual A, D Register With Pre-adder 25x18 signed multiplier 48-bit add/subtract/accumulate 48-bit logic operations Pipeline registers for high speed Pattern detector SIMD operations (12/24 bit) Cascade paths for wide functions Pre-adder 25x18 signed multiplier 48-bit add/subtract/accumulate 48-bit logic operations Pipeline registers for high speed Pattern detector SIMD operations (12/24 bit) Cascade paths for wide functions Pre-adder

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Normal or 17-bit right shifted with MSB fill for multi-precision arithmetic X, Y, and Z Multiplexers Adder/subtractor operates on X, Y, Z and CIN operands –Table shows basic operations X, Y, and Z multiplexers allow for dynamic OPMODEs Multiplier output requires both X and Y multiplexers ALUMODEOperation 0000Z + X + Y + CIN 0001-Z + (X + Y + CIN) – Z – X – Y – CIN – Z – (X + Y + CIN) OthersLogic Operations

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Apply Your Knowledge 1) Given this OPMODE table, what is the OPMODE for the following functions? –C + A:B –A*B + C –P + C + PCIN OPMODE Controls the behavior of X, Y, and Z multiplexers

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Dual B Register B input to multiplier is controlled by INMODE[4] –Dynamically selects B1/B2 pipeline level B input to X MUX and BCOUT cascade outputs are statically controlled by bitstream options B1 B 18 B2 BCIN B MULT BCOUT X MUX 18 INMODE[4] Bitstream Controlled Dynamically Controlled

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Dual A, D, Registers and Pre-Adder A1 A 30 A2 ACIN A MULT ACOUT X MUX D25 30 DAD INMODE[0] INMODE[1] INMODE[2] INMODE[3] 25 A input to multiplier is controlled by INMODE[3:0] –Dynamically selects A1/A2 pipeline level –Dynamically selects add/subtract –Dynamically selects Zero for A or D ACOUT and X MUX input are statically controlled Bitstream Controlled Dynamically Controlled

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X Y Z P 0 P A:B 1 0 P PCIN 0 C ALUMODE[3:0] OPMODE[3:0] Logic Unit ModeOPMODE[3:2]ALUMODE[3:0] X XOR Z X XNOR Z X XNOR Z X XOR Z X AND Z X AND (NOT Z) X NAND Z (NOT X) OR Z X XNOR Z X XOR Z X XOR Z X XNOR Z X OR Z X OR (NOT Z) X NOR Z (NOT X) AND Z Two-Input Logic Functions 48-bit logic operations –XOR, XNOR, AND, NAND, OR, NOR, NOT ALUMODEs

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Pattern Detect and SIMD Pattern detection –Pattern and mask operation on output of adder Pattern can be constant (set by attribute) or C input –Enables Symmetric rounding for multi-precision operations Convergent rounding Saturation Accumulator terminal count SIMD operations –48-bit adder broken into 2x24 bits or 4x12 bits Allows two or four independent additions to be done –Carry bits brought out independently and disabled between sections Carry bits can be cascaded between DSP48E1 slices = P C or MC

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Cascade Paths Cascade paths exist from each DSP48E1 slice to the slice above it –A input, B input, P output, and carry out P cascade path can be shifted by 17 bits by slice above Enables common functions with little or no additional resources –Wider accumulators, wider multipliers, complex multipliers, and FIR filters –Example: 35-bit x 25-bit multiplier with two DSP48E1s 0,B[16:0] A[24:0] B[34:17] B P B P A SHIFT 17 P[16:0] = OUT[16:0] P[42:0] = OUT[59:17] ACIN DSP48_1 OPMODE ALUMODE 0000 DSP48_0 OPMODE ALUMODE 0000

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DSP Review 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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Summary All 7 series FPGAs contain the same DSP48E1 cell –The DSP48E1 is identical to the one used in the Virtex-6 FPGA The DSP48E1 cell has the following features –25x18 signed multiplier –48-bit add/subtract/accumulate –Pipeline registers for high speed –Pattern detector –SIMD operators –Cascade paths –25 bit pre-adder –Dynamic pipeline control

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Trademark Information Xilinx is disclosing this Document and Intellectual Property (hereinafter “the Design”) to you for use in the development of designs to operate on, or interface with Xilinx FPGAs. Except as stated herein, none of the Design may be copied, reproduced, distributed, republished, downloaded, displayed, posted, or transmitted in any form or by any means including, but not limited to, electronic, mechanical, photocopying, recording, or otherwise, without the prior written consent of Xilinx. Any unauthorized use of the Design may violate copyright laws, trademark laws, the laws of privacy and publicity, and communications regulations and statutes. Xilinx does not assume any liability arising out of the application or use of the Design; nor does Xilinx convey any license under its patents, copyrights, or any rights of others. You are responsible for obtaining any rights you may require for your use or implementation of the Design. Xilinx reserves the right to make changes, at any time, to the Design as deemed desirable in the sole discretion of Xilinx. Xilinx assumes no obligation to correct any errors contained herein or to advise you of any correction if such be made. Xilinx will not assume any liability for the accuracy or correctness of any engineering or technical support or assistance provided to you in connection with the Design. THE DESIGN IS PROVIDED “AS IS" WITH ALL FAULTS, AND THE ENTIRE RISK AS TO ITS FUNCTION AND IMPLEMENTATION IS WITH YOU. YOU ACKNOWLEDGE AND AGREE THAT YOU HAVE NOT RELIED ON ANY ORAL OR WRITTEN INFORMATION OR ADVICE, WHETHER GIVEN BY XILINX, OR ITS AGENTS OR EMPLOYEES. XILINX MAKES NO OTHER WARRANTIES, WHETHER EXPRESS, IMPLIED, OR STATUTORY, REGARDING THE DESIGN, INCLUDING ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND NONINFRINGEMENT OF THIRD-PARTY RIGHTS. IN NO EVENT WILL XILINX BE LIABLE FOR ANY CONSEQUENTIAL, INDIRECT, EXEMPLARY, SPECIAL, OR INCIDENTAL DAMAGES, INCLUDING ANY LOST DATA AND LOST PROFITS, ARISING FROM OR RELATING TO YOUR USE OF THE DESIGN, EVEN IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE TOTAL CUMULATIVE LIABILITY OF XILINX IN CONNECTION WITH YOUR USE OF THE DESIGN, WHETHER IN CONTRACT OR TORT OR OTHERWISE, WILL IN NO EVENT EXCEED THE AMOUNT OF FEES PAID BY YOU TO XILINX HEREUNDER FOR USE OF THE DESIGN. YOU ACKNOWLEDGE THAT THE FEES, IF ANY, REFLECT THE ALLOCATION OF RISK SET FORTH IN THIS AGREEMENT AND THAT XILINX WOULD NOT MAKE AVAILABLE THE DESIGN TO YOU WITHOUT THESE LIMITATIONS OF LIABILITY. The Design is not designed or intended for use in the development of on-line control equipment in hazardous environments requiring fail-safe controls, such as in the operation of nuclear facilities, aircraft navigation or communications systems, air traffic control, life support, or weapons systems (“High-Risk Applications”). Xilinx specifically disclaims any express or implied warranties of fitness for such High-Risk Applications. You represent that use of the Design in such High-Risk Applications is fully at your risk. © 2012 Xilinx, Inc. All rights reserved. XILINX, the Xilinx logo, and other designated brands included herein are trademarks of Xilinx, Inc. All other trademarks are the property of their respective owners.

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7 Series DSP Resources Part 3

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Objectives After completing this module, you will be able to: Describe the basic usage models of DSP slices Describe the DSP slice in the 7 series FPGAs

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DSP Overview 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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Pre-Adder The pre-adder can add or subtract the two 25-bit operands on the A and the D inputs before the result drives the multiplier Benefits –Perfect for operations using symmetrical coefficients –Doubles the efficiency of symmetric FIR and symmetric IIR and transpose convolution filters –Half the power consumption compared to architectures without a pre-adder –Smaller total logic footprint –A small change with a big benefit

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Symmetrical Filters When the coefficients are symmetrical –The pre-adders either reduce the number of multiplications by 50% or double the sample rate –Factorizing the taps replaces one multiplication by a pre-addition (or pre-subtraction) k13k17 Non symmetrical filter (k13≠k17) : (tap13×k13) + (tap17×k17) Symmetrical filter (k13=k17) : (tap13+tap17) × k13 2 mults and one post-add 1 pre-add Symmetrical Filter Example 1 mult Direct benefit: saves 50% of the DSP slices

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Six-Tap Transpose FIR Filter Without Pre-Adder Uses six legacy DSP slices (without pre-adder) XX X X k0k0 k1k1 k2k2 k1k y(n-4) z -1 X k0k0 + 0 X k2k2 + z -2 x(n-2) x(n-3) x(n-4) x(n-5) x(n-6)x(n-7) x(n)

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Six-Tap Transpose FIR Filter Using the Pre-Adder Optimized implementation supported by XST using only three slices instead of six x(n) X X k2k2 k1k1 ++ y(n-4) z -2 z -1 X k0k0 + 0 z -2 z -1 + z -2 + z -1 + x(n-7)+x(n-2) x(n-6)+x(n-3) x(n-5)+x(n-4)

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Dynamic Pipeline Control The 7 series FPGA DSP slice has dynamic pipeline control on the A and B registers –User can select which of the two pipeline registers to use for calculations on a clock-by-clock basis Benefits –Allows an operation to reuse the same operand in subsequent cycles

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Application: Sequential Complex Multiply Complex Multiply (A + ai) * (B + bi) = (AB-ab) + (Ab+aB)i Use the two AB registers to locally store the real and imaginary parts of the operands – Read each component of the complex operands out of memory only once – Fewer memory reads because A, a, B, and b are then stored locally Dynamic routing is controlled by an FSM updating the INMODE register on the fly Needs only four clocks for 18-bit data using a single slice

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Application: Sequential Large Multiply Four-step large multiplication 42 bits * 34 bits = (A:a) * (B:b) = A*B + sh17(A*0b + B* a + sh17(0b* a) Needs only four clocks for 18-bit data using a single slice

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DSP Review 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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IP Support and Inference Some basic functions can be inferred –Example: Multiplier, Multiply-Accumulate, … Other functions are supported through the CORE Generator™ interface –Examples: FFT, FIR Compiler, and DDS Compiler New IP cores become available with each service pack –Visit the IP Center for information on the newest IP cores

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Example: 16x16 Multiplier, inputs registered once, -- outputs twice -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (xxx,01,01): p1 <= a1*b1; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then a1 '0'); b1 '0'); p '0'); elsif ce = '1' then a1 <= a; b1 <= b; p <= p1; end if; end process; Example: 16x16 Multiplier, inputs registered once, -- outputs twice -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (xxx,01,01): p1 <= a1*b1; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then a1 '0'); b1 '0'); p '0'); elsif ce = '1' then a1 <= a; b1 <= b; p <= p1; end if; end process; /////////////////////////////////////////////////////////////////// // Example: 16x16 Multiplier, inputs registered // once, outputs twice // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (xxx,01,01):0 /////////////////////////////////////////////////////////////////// assign p1 = a1*b1; clk) if (rst == 1'b1) begin a1 <= 0; b1 <= 0; p <= 0; end else if (ce == 1'b1) begin a1 <= a; b1 <= b; p <= p1; end /////////////////////////////////////////////////////////////////// // Example: 16x16 Multiplier, inputs registered // once, outputs twice // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (xxx,01,01):0 /////////////////////////////////////////////////////////////////// assign p1 = a1*b1; clk) if (rst == 1'b1) begin a1 <= 0; b1 <= 0; p <= 0; end else if (ce == 1'b1) begin a1 <= a; b1 <= b; p <= p1; end Inferring a 16 x 16 Multiplier

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Example: Multiply add function, single level of register -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (011,01,01): p1 <= a*b + c; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then p '0'); elsif ce = '1' then p <= p1; end if; end process; Example: Multiply add function, single level of register -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (011,01,01): p1 <= a*b + c; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then p '0'); elsif ce = '1' then p <= p1; end if; end process; //////////////////////////////////////////////////////////// // Example: Multiply add function, single level of register // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (011,01,01):0 //////////////////////////////////////////////////////////// assign p1 = a*b + c; clk) if (rst == 1'b1) p <= 0; else if (ce == 1'b1) begin p <= p1; end //////////////////////////////////////////////////////////// // Example: Multiply add function, single level of register // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (011,01,01):0 //////////////////////////////////////////////////////////// assign p1 = a*b + c; clk) if (rst == 1'b1) p <= 0; else if (ce == 1'b1) begin p <= p1; end Inferring a Multiply Accumulate (MACC)

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Example: 16 bit adder 2 inputs, input and output -- registered once -- Mapping to DSP48 should be driven by timing as -- DSP48 are limited resources. The -use_dsp48 XST -- switch must be set to YES -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (000,11,11):0 or -- (011,00,11): p1 <= a1 + b1; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then p '0'); a1 '0'); b1 '0'); elsif ce = '1' then a1 <= a; b1 <= b; p <= p1; end if; end process; Example: 16 bit adder 2 inputs, input and output -- registered once -- Mapping to DSP48 should be driven by timing as -- DSP48 are limited resources. The -use_dsp48 XST -- switch must be set to YES -- Matches 1 DSP48 slice -- OpMode(Z,Y,X):Subtract -- (000,11,11):0 or -- (011,00,11): p1 <= a1 + b1; process (clk) is begin if clk'event and clk = '1' then if rst = '1' then p '0'); a1 '0'); b1 '0'); elsif ce = '1' then a1 <= a; b1 <= b; p <= p1; end if; end process; //////////////////////////////////////////////////////////////////////// // Example: 16 bit adder 2 inputs, input and output // registered once // Mapping to DSP48 should be driven by timing as // DSP48 are limited resources. The -use_dsp48 XST // switch must be set to YES // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (000,11,11):0 or // (011,00,11):0 //////////////////////////////////////////////////////////////////////// assign p1 = a1 + b1; clk) if (rst == 1'b1) begin p <= 0; a1 <= 0; b1 <= 0; end else if (ce == 1'b1) begin a1 <= a; b1 <= b; p <= p1; end //////////////////////////////////////////////////////////////////////// // Example: 16 bit adder 2 inputs, input and output // registered once // Mapping to DSP48 should be driven by timing as // DSP48 are limited resources. The -use_dsp48 XST // switch must be set to YES // Matches 1 DSP48 slice // OpMode(Z,Y,X):Subtract // (000,11,11):0 or // (011,00,11):0 //////////////////////////////////////////////////////////////////////// assign p1 = a1 + b1; clk) if (rst == 1'b1) begin p <= 0; a1 <= 0; b1 <= 0; end else if (ce == 1'b1) begin a1 <= a; b1 <= b; p <= p1; end Inferring a 2-Input Adder

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Example: Loadable Multiply Accumulate with one level -- of registers -- Map into 1 DSP48 slice -- Funtion: OpMode(Z,Y,X):Subtract -- - load (011,00,00): mult_acc (010,01,01):0 -- Restriction: Since C input of DSP48 slice is used, then -- adjacent DSP cannot se a different c input (c input are -- shared between 2 adjacent DSP48 slices) -- Expected mapping: -- AREG: no, BREG: no, CREG: no, MREG: no, PREG: yes with load select p_tmp <= signed(c) when '1', p_reg + a1*b1 when others; process(clk) begin if clk'event and clk = '1' then if p_rst = '1' then p_reg '0'); a1 '0'); b1 '0'); elsif p_ce = '1' then p_reg <= p_tmp; a1 <= signed(a); b1 <= signed(b); end if; end process; p <= std_logic_vector(p_reg); Example: Loadable Multiply Accumulate with one level -- of registers -- Map into 1 DSP48 slice -- Funtion: OpMode(Z,Y,X):Subtract -- - load (011,00,00): mult_acc (010,01,01):0 -- Restriction: Since C input of DSP48 slice is used, then -- adjacent DSP cannot se a different c input (c input are -- shared between 2 adjacent DSP48 slices) -- Expected mapping: -- AREG: no, BREG: no, CREG: no, MREG: no, PREG: yes with load select p_tmp <= signed(c) when '1', p_reg + a1*b1 when others; process(clk) begin if clk'event and clk = '1' then if p_rst = '1' then p_reg '0'); a1 '0'); b1 '0'); elsif p_ce = '1' then p_reg <= p_tmp; a1 <= signed(a); b1 <= signed(b); end if; end process; p <= std_logic_vector(p_reg); /////////////////////////////////////////////////////////////////////////////// // Example: Loadable Multiply Accumulate with one level // of registers // Map into 1 DSP48 slice // Funtion: OpMode(Z,Y,X):Subtract // - load (011,00,00):0 // - mult_acc (010,01,01):0 // Restriction: Since C input of DSP48 slice is used, then // adjacent DSP cannot use a different c input (c input are // shared between 2 adjacent DSP48 slices) // Expected mapping: // AREG: no, BREG: no, CREG: no, MREG: no, PREG: yes /////////////////////////////////////////////////////////////////////////////// assign p_tmp = load ? c:p + a1*b1; clk) if (p_rst == 1'b1) begin p <= 0; a1 <=0; b1 <=0; end else if (p_ce == 1'b1) begin p <= p_tmp; a1 <=a; b1 <= b; end /////////////////////////////////////////////////////////////////////////////// // Example: Loadable Multiply Accumulate with one level // of registers // Map into 1 DSP48 slice // Funtion: OpMode(Z,Y,X):Subtract // - load (011,00,00):0 // - mult_acc (010,01,01):0 // Restriction: Since C input of DSP48 slice is used, then // adjacent DSP cannot use a different c input (c input are // shared between 2 adjacent DSP48 slices) // Expected mapping: // AREG: no, BREG: no, CREG: no, MREG: no, PREG: yes /////////////////////////////////////////////////////////////////////////////// assign p_tmp = load ? c:p + a1*b1; clk) if (p_rst == 1'b1) begin p <= 0; a1 <=0; b1 <=0; end else if (p_ce == 1'b1) begin p <= p_tmp; a1 <=a; b1 <= b; end Inferring a Loadable MACC

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DSP Review 7 Series FPGA DSP Slice Pre-Adder and Dynamic Pipeline Control Advantages IP Support and Inference Summary Lessons

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Summary All 7 series FPGAs contain the same DSP48E1 cell –The DSP48E1 is identical to the one used in the Virtex-6 FPGA The DSP48E1 cell has the following features –25x18 signed multiplier –48-bit add/subtract/accumulate –Pipeline registers for high speed –Pattern detector –SIMD operators –Cascade paths –25 bit pre-adder –Dynamic pipeline control DSP48E1 slices can be inferred, instantiated or accessed using IP cores

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Where Can I Learn More? 7 Series DSP48E1 Slice User Guide –Slice description –Design consideration How to design to optimize for power and performance How to use advanced design techniques –Design recommendations for XST This guide has example inferences of many architectural resources –XST User Guide Refer to the Coding Techniques chapter Xilinx Education Services courses –www.xilinx.com/training Xilinx tools and architecture courses and other Free videos!

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