OH! Open Hardware for Chip Designers

April 26, 2021 · View on GitHub

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OH! Open Hardware for Chip Designers

Introduction

!!! WARNING!!!

Main branch is Work In Progress (ie broken)
For a stable version, seee Tag V1.0

OH! is an open-source library of hardware building blocks based on silicon proven design practices at 0.35um to 28nm. The library is being used by Adapteva in designing its next generation ASIC.

The library is written in standard Verilog (2005) and contains over 25,000 lines of Verilog code, over 150 separate modules. Examples of functionality include: FIFOs, SPI (master/slave), GPIO, high speed links, memories, clock circuits, synchronization primitives,interrupt controller, DMA.

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Philosophy

Make it work
Make it simple
Make it modular

Modules

FOLDER	STATUS	DESCRIPTION
accelerator	FPGA	Accelerator tutorial
axi	FPGA	AXI master and slave interfaces
chip	SI	Chip design reference flow
common	SI	Library of basic components
edma	HH	DMA engine
elink	SI	Point to point LVDS link
emailbox	FPGA	Mailbox with interrupt output
emesh	SI	Emesh interface circuits
emmu	FPGA	Memory translation unit
etrace	HH	Logic Analyzer
gpio	HH	General Purpose IO
mio	HH	Lightweight parallel link
pic	SI	Interrupt controller
parallella	FPGA	Parallella FPGA logic
risc-v	HH	RISC-V implementation
spi	HH	SPI master/slave
xilibs	FPGA	Xilinx simulation models

NOTES:

"SI"= Silicon validated
"FPGA" = FPGA validated
"HH" = Hard hat area (work in progress)

How to simulate

Scripts are located in the './scripts' directory.

./scripts/build.sh gpio/dv/dut_gpio.v         # compile gpio testbench (example)
./scripts/sim.sh gpio/dv/tests/test_basic.emf # run "test_basic.emf" test
./scripts/view.sh                             # open the waveform with gtkwave

Short-cut:

Builds $name/dv/dut_$ name.v
Runs test $name/dv/tests/test_basic.emf

./run.sh accelerator  # Run accelerator simulation
./run.sh elink        # Run elink simulation
./run.sh emailbox     # Run emailbox simulation
./run.sh emmu         # Run emmu simulation
./run.sh gpio         # Run gpio simulation
./run.sh mio          # run mio simulation
./run.sh spi          # Run spi simulation
./run.sh pic          # Run pic simulation

How to build

TBD

Design Guide

Separate circuit from logic
Separate control from the datapath
Separate configuration from design
Separate design from testbench
Separate testbench from test (data)
Use 64b boundaries for scalable registers (when reasonable)
Place multi bit fields on nibble boundaries (when reasonable)
Make reset values "0"
Only reset register if absolutely necessary
More to come...

Coding Guide

Max 80 chars per line
One input/output statement per line
Only single line // comments, no /../
Use vector sizes in every statement, ie "assign a[7:0] = myvec[7:0];"
Use parameters for reusability and readability
Use many short statements in place of one big one
Define wires/regs at beginning of file
Align input names/comments in column like fashion
Avoid redundant begin..end statements
Capitalize macros and constants
Use lower case for all signal names
User upper case for all parameters and constants
Use y down to x vectors
Use a naming methodology and document it
Comment every module port
Do not hard code numerical values in body of code
Keep parameter names short
Use common names: nreset, clk, din, dout, en, rd, wr, addr, etc
Make names descriptive, avoid non-common abbreviations
Make names as short as possible, but not shorter
Use short named generate blocks "g0, g1, etc"
Inside generate blocks use short "i" for instance
Use _ in constants over 4 bits (eg: 8'h1100_1100)
One module per file
Use ".vh" suffix for header files,
Use ".v" for verilog source files
Use `include files for constants
Use `ifndef _CONSTANTS_V to include file only once
No timescales in design files (only in testbench)
No delay statements in design
No logic statements in top level design structures
Prefer parameters in place of global defines
Do not use casex
Use active low reset
Avoid redundant resets
Avoid heavily nested if, else statements
Don't use defparams, place #(.DW(DW)) in module instantation
With parameters, NEVER us this instantiation: "mux3 #(32) U2 (...)"
Always use connection by name (not by order) in module instantiatoin
Parametrize as much as possible but not more
Place a useful comment every 5-20 lines
If you are going to use async reset, use oh_rsync.v
Use for loops to reduce bloat and to improve readability
If you have to mix clock edges, isolate to discrete modules
Use nonblocking (<=) in all sequential statements
Use default statements in all case statements
Don't use proprietary EDA tool pragmas (use parameters)
Only use synthesizable constructs
Use $signed() for arithmetic operations on signed types .
Allowed keywords: assign, always, input, output, wire, reg, module, endmodule, if/else, case, casez, ~,|,&,^,==, >>, <<, >, <,?,posedge, negedge, generate, for(...), begin, end, $signed,

Documentation Guide

Write docs in markdown
Specify which registers are reset
Put lsb on right side, lsb is bit zero
Indicate type (read/write/etc)
Indicate what
All signal should be summarized in a table (markdown)
All signals should have waveforms (wavedrom)
List internal block hierarhcy (need script for this)
Unused/reserved bits in all register should be written as zero
In tables, place registers in address order
In description section, place registeres in alphabetical order
Include links in table to descriptions
Include "internal register map"
Base address of chip/block
Table of interrupts..
Show how to compile..
Show how to simulate...
Show how to synthesize/build..
Show how to use..

Tapeout Checklist

HERE

License

The OH! repository source code is licensed under the MIT license unless otherwise specified. See LICENSE for MIT copyright terms. Design specific licenses can be found in the folder root (eg: aes/LICENSE)

picture-license