RTL design in python:

Transcription

1 RTL design in python: porting the mmips Jos Huisken June 25 th, 2013

2 What is Python?

3 What is Python? A general purpose programming language Growing in popularity Interpreted language (bytecode-interpretive) Multi-paradigm Clean object-oriented Functional in the LISP tradition Structural (procedural-imperative) Extremely readable syntax Very high-level Lists Dictionaries (associative arrays) Extensive documentation

4 What is MyHDL? A Python package which enables hardware description Open-source project Batteries included (more on this later)

5 MyHDLExtends Python MyHDLis Python Using Python constructs to extend Object Oriented Signal, intbv Generators Micro-thread like, enables concurrency behavior Resumable functions that maintain state Decorators Meta-programming Macro mechanism Modifies a function /

6 Why use MyHDL Manage Complex Designs New to Digital Hardware Design Scripting Languages Intensively Used Modern Software Development Techniques for Hardware Design Algorithm Development and HDL Design in a Single Environment Require Both Verilog and VHDL VHDL Too Verbose SystemVerilog Too Complicated You Been TCL dtoo much

7 What MyHDLis NOT Not arbitrary Python to silicon Not a radically new approach Not a synthesis tool Not an IP block library Not only for implementation Not well suited for accurate time simulation

8 Abstraction Levels ADC ADC System Level Algorithmic Level Register Transfer x x Decimation Filter Decimation Filter I reset=reset) def hdl(): sum.next = a + b sin cos NCO Logic Level Transistor Level Geometry Level AND OR

9 Register Transfer Register Transfer Level (RTL) abstraction This is the commonly excepted description of mainstream HDLs: Verilog and VHDL Describes the operations between registers MyHDLoperates at the Register Transfer Level (RTL) MyHDL extends Python for hardware description

10 MyHDLTypes intbv Bit vector type, an integer with bit vector properties Signal Deterministic communication, see it as a VHDL signal Convertible types intbv bool int tuple of int list of booland list of intbv

11 MyHDLGenerators A Python generator is a resumable function Generators are the core of MyHDL Provide the similar functionality as a VHDL process or Verilog always block yieldin a generator

12 Python generator: Fibonacci 7 # function version 8 def fibon(n): 9 a = b = 1 10 result = [] 11 for i in xrange(n): 12 result.append(a) 13 a, b = b, a + b 14 return result 7 # generator version 8 def fibon(n): 9 a = b = 1 10 result = [] 11 for i in xrange(n): 12 yield a 13 a, b = b, a + b 15 fibon(8) 16[1, 1, 2, 3, 5, 8, 13, 21] 14for x in fibon(8): 15 print x,

13 MyHDLDecorators MyHDL Decorators creates ready-to-simulate generators from local @always_comb

14 Python decorator 8 def myfunc(): 9 return 10# is equivalent to 11def myfunc(): 12 return 13myfunc = mydecorator(myfunc) A decoratoris a function (mydecorator) that takes a function object as an argument, and returns a function object as a return just syntactic sugar 7 def verbose(origfunc): 8 # make new func 9 def newfunc(*args, **kwargs): 10 print entering, origfunc. name 11 origfunc(*args, **kwargs) 12 print exiting, origfunc. name 13 return newfunc 14@verbose 15def myfunc(s): 16 print s 17myfunc( hoi ) 18entering myfunc 19hoi 20exiting myfunc

15 MyHDLFlow myhdl package import myhdl python source verification modeling RTL myhdl simulator python compiler tools myhdl conversion VCD cosim Verilog / VHDL python run-time (cpython, pypy) RTL synthesis verification results architecture trade-offs statistics Verilog simulation gates wave FPGA IC

16 MyHDLConversion MyHDL has a convertible subset Convert to Verilog Convert to VHDL Pragmatic Standard FPGA / ASIC flow after conversion

17 Anatomy of a MyHDLModule module name ports and parameters event definition elaboration code sequential block generator name return list of generators logic for the block

18 Simple adder in myhdl

19 A register

20 ALU waveform, using gtkwave

21 Verilog co-simulation Icarus Verilog Cadence ncsim Cadence ncsim, CMOS90 netlist Select icarus/verilog implementation:

22 Generated: add.v

23 mmipsin MyHDL Single cycle mini-mini MIPS Multi cycle mini MIPS

24 Ecosystem import pylab import matplotlib

25 Digital Filter x[n] 1.23 b T 1.23 y[n] z -1 b a1 z -1 z -1 b a2 z -1

26 IIR Type I Digital Filter 1 def m_iir_type1(clock,reset,x,y,ts,b=none,a=none): 2 # make sure B and A are ints and make it a ROM (tuple of ints) 3 b0,b1,b2 = map(int,b) 4 a0,a1,a2 = map(int,a) 5 6 ffd = [Signal(intbv(0, min=x.min, max=x.max)) for ii in (0,0)] 7 fbd = [Signal(intbv(0, min=x.min, max=x.max)) for ii in (0,0)] 8 # intermidiate result, resize from here 9 ysop = Signal(intbv(0, min=dmin, max=dmax)) 10 reset=reset) 12 def hdl(): 13 if ts: 14 ffd[1].next = ffd[0] 15 ffd[0].next = x fbd[1].next = fbd[0] 18 fbd[0].next = ysop//am # truncate (>>) # extra pipeline on the output at clock 21 ysop.next = (b0*x) + (b1*ffd[0]) + (b2*ffd[1]) - \ 22 (a1*fbd[0]) - (a2*fbd[1]) # truncate to the output word format 25 y.next = ysop//am # truncate (>>) return hdl

27 Simulation

28 Test Frameworks Test frameworks are easy Enables new levels or reuse Test Driven Design (TDD) Existing test environments py.test nose unittest

29 Example: fpgalink 4 test 1 host SW adapters + models FPGA Logic fgpalink logic logic logic models checkers 7 app libfpgalink USB controller logic transducers Test code Application code Host interface software Connect the host software to the DUT Host driver + USB controller FPGA logic (HDL) External models and checkers Physical transducers

30 Conclusion Python Easy to learn Batteries included MyHDL Hardware description in Python Powerful environment, ecosystem Verification simplified and fun mmips Ported from SystemC Simulated and Co-Simulated, not fully verified Synthesized: ISE (untested) and Cadence rc(co-simulated) Python: allows ( ) matlab style interaction

31 Short MyHDLHistory Jan Decaluwe Creator of MyHDL Founder & Board Member Easic Created MyHDLbetween First Release on SourceForge Sep 30, MyHDL ASIC n/digmac.html

32 Acknowledgement You guys for hosting and providing the mmips Christopher Felton Several slides came from him!

33 Resources And an invitation to join (still) password protected: Any Further Questions??