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The Scalable Configurable Instrument Processor

The Scalable Configurable Instrument Processor. John R. Hayes Johns Hopkins University Applied Physics Laboratory john.hayes@jhuapl.edu. Instrument processors require low power, small footprint, etc. Few processors meet these requirements Design our own using VHDL and FPGAs

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The Scalable Configurable Instrument Processor

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  1. The Scalable Configurable Instrument Processor John R. Hayes Johns Hopkins University Applied Physics Laboratory john.hayes@jhuapl.edu 1

  2. Instrument processors require low power, small footprint, etc. Few processors meet these requirements Design our own using VHDL and FPGAs Architectural influences: APL’s FRISC (Freja, Flare Genesis) Harris RTX2010 (NEAR, ACE, MESSENGER, New Horizons, etc.) Introduction 2

  3. SCIP Processor Features • Stack Architecture: N op T->T (RTX) • 16 or 32-bit Internal Data Path • 16-bit Instruction OpCode • ALU/Condition Architecture (FRISC3/4) • Multiply/Divide Steps (FRISC4) • Barrel Shifter (FRISC4) • Stack Caches (FRISC3/4) • Memory-Mapped I/O 3

  4. Scalability • Data path, i.e. buses, ALU, barrel shifter can be 16 or 32 bits wide • Buses scale trivially in VHDL: • bus_x: in unsigned(DBITS-1 downto 0); • ALU based on function blocks with 1-level of carry look-ahead scales easily • Multiplier would not scale well; instead use Booth multiply step; “scaling” done in software 4

  5. More Scalability • Barrel shifter (based on funnel shifter) uses N*log(N) resources -- Funnel shifter. process(a, b, count) variable t: unsigned(2*DBITS-1 downto 0); begin t := a & b; for i in 0 to DLBITS-1 loop if count(i) = '1' then t := to_unsigned(0, 2**i) & t(2*DBITS-1 downto 2**i); end if; end loop; result <= t(DBITS-1 downto 0); end process; 5

  6. Configurability • SCIP library • SCIP (DBITS=16 or 32, ABITS=up to 32) • Clock generator (WBITS) • AMBA APB bridge (ABITS, DBITS) • AMBA APB component library • Interrupt controller (INTS) • UART (DATABITS, STOPBITS, DIV) • Parallel ports (BITS) • Others: I2C-subset, watchdog, etc. 6

  7. Configuring a System on a Chip (SoC) • All components except decoders and memory controller are from libraries • A basic SoC, processor, interrupt controller, and UART, is ~500 lines of VHDL 7

  8. Instruction Set 8

  9. 16-Bit Version • Adds Code Page and Data Page Registers to supply upper address bits • Adds far/near mode bit and special instructions to set/reset mode • Not compatible with RTX object code, but most RTX source code runs • Most I/O routines must be rewritten • APL’s common instrument software library has been ported 9

  10. 32-Bit Version • Adds Long Subroutine Call instruction • Adds 32-bit option to Load/Store instructions • Adds scale to Long Immediate instruction; any 32-bit literal can be constructed with at most two instructions 10

  11. Implementation: Simulation • Port cross-compilers to SCIP, 16-bit and 32-bit versions • Write architectural simulator in C • Validate architecture, compiler, and simulator • Translate C into VHDL • Use simulator to generate VHDL test bench • Simulate VHDL test bench to validate translation 11

  12. Implementation: SCIP Synthesis Area Usage • Synthesize processor using Synplify Pro • Synthesize 16-bit SCIP and 32-bit SCIP for three similar parts 12

  13. Implementation: Xilinx • Xilinx Spartan-3 Starter Kit Board • Board has 3S200 FPGA and 1 MB SRAM • SCIP-16 with UART • Usage: 8% (+ RAM) / 39% • SCIP-32 with UART • Usage: 14% (+ RAM) / 65% • Runs all test programs 13

  14. Implementation: New Horizons (NH) Demo • Build-up flight-spare NH processor board • Remove RTX2010 processor • Replace NH Actel (SX72) with: • SCIP-16, clock gen., memory I/F, etc • NH S/C I/F, watchdog, I2C subset, etc. • Interrupt control, test port UART, etc. • Measure power, etc. 14

  15. Implementation: NH RTX Processor Board 15

  16. Implementation: NH SCIP Processor Board 16

  17. Implementation: NH SCIP Results • Actel (SX72) usage: 59 / 60% • Running at 6 MHz (instruction rate) • Board powered from external 5V (Actel core 2.5 V from on-board regulator) 17

  18. Implementation: V-Slit Demo • Redesign of NH RTX processor board • Replace RTX2010 with QuickLogic QL6325: • SCIP-16, clock gen., memory I/F, etc • QL6325 -> Aeroflex UT6325 path to flight • Replace Actel SX72 with SX32: • NH S/C I/F, etc. • Interrupt control, test port UART, etc. • Measure power, etc. 18

  19. Implementation: V-Slit SCIP Processor Board 19

  20. Implementation: V-Slit Results • QuickLogic (QL6325) usage: 52 / 45 % • Running at 6 MHz (instruction rate) • Board powered from external 3.3 and 2.5V (QuickLogic and Actel share 2.5 V) 20

  21. Summary • Architecture validated • Implementations on Xilinx, Actel, and QuickLogic tested • SCIP-16 provides replacement for RTX2010; SCIP-32 provides growth path • SCIP use planned on several upcoming flight instruments 21

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