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OOP for Hardware Verification ̶ Demystified!

OOP for Hardware Verification ̶ Demystified!

Mike MintzCo-author, Hardware Verification with C++

and Hardware Verification with SystemVerilogmike@trusster.com

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Overview• Common Currency

• Data Abstraction

• Virtual Functions

• Base Classes

• Q&A

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Common Currency

generator checker

monitordriver

DUT

*There is nothing new under the sun.

Sub sole nihil novi est.*

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Data Abstraction

• Procedural code has separate data structures and functions.

• OOP moves the functions into the data structure,

• Every possible function for that structure is now in one place.

• This works well for a driver.

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Data Abstraction – Code DetailsProcedural Data Abstraction

begin

usb_driver driver;

usb_init (&driver);

usb_enumerate (&driver);

usb_send (&driver, 0, {0,12}, 2);

end

begin usb_driver driver;driver. init ();driver.enumerate ();driver.send (0, {0,12}, 2);

end

struct usb_driver {wire d_plus, d_minus;}

void usb_init (usb_driver * d);

void usb_send_packet (usb_driver * d, int type, int* data, int length);

void usb_enumerate (usb_driver * d);

struct usb_driver {

wire d_plus, d_minus;

void init ();

void send_packet (int type, int* data, int length);

void enumerate ();

};

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Virtual Function

• Is a run-time function call.• Is the “I don’t know” function.• Great for separating concerns

(and increasing portability).• This works well for a monitor.

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Virtual FunctionsMonitor class Derived for printing

struct usb_printer: public usb_monitor {

virtual void packet_completed (int length, int* data) {

for (int i(0); i < length; ++i) {

printf (“Packet [%d]:0x%x\n”, i, data[i]);

}

}

};

Derived for checkerstruct usb_checker : public usb_monitor {

virtual void packet_completed (int length, int* data) {

checker_->check (length, data);

}

checker* checker_;

};

Derived for channelstruct usb_monitor_agent : public usb_monitor {

virtual void packet_completed (int length, int* data) {

channel_->put (data_packet (length, data));

}

usb_channel* channel_;

};

struct usb_monitor {

wire d_plus, d_minus;

void start_monitor_thread ();

virtual void packet_completed (int length, int* data) =0;

};

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Base Class

• Is a class with one or more virtual methods.

• Is the “follow my lead” class.• Sets up a framework or interface.• This works well for a test irritator.

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Base Classes – Code Details

struct irritator {

virtual void out_of_reset () =0;

virtual void start () =0;

virtual void stop () =0;

virtual void wait_for_completion () =0;

};

Irritator class Derived for USB

Derived for PCIE Derived for Ethernet

struct usb_irritator : public irritator {

virtual void out_of_reset ();

virtual void start ();

virtual void stop ();

virtual void wait_for_completion ();

};

struct pcie_irritator: public irritator {

virtual void out_of_reset ();

virtual void start ();

virtual void stop ();

virtual void wait_for_completion ();

};

struct ethernet_irritator: public irritator {

virtual void out_of_reset ();

virtual void start ();

virtual void stop ();

virtual void wait_for_completion ();

};

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Using OOP – Truss Top-Level Components

Verification Component Hierachy

verification top

test watchdog timer

testbench

test component

irritator

chip

C++HDL

Source: Hardware Verification with C++, page 95, page 100

class verification_component {

public:

verification_component (const std::string&);

virtual void randomize () = 0;

virtual void time_zero_setup () = 0;

virtual void out_of_reset (reset r) = 0;

virtual void start () = 0;

virtual void wait_for_completion () = 0;

virtual void report (const std::string) = 0;

};

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The “Dance”new()

WatchdogTest Testbenchverification_top

randomize()

time_zero_setup()

out_of_reset()

start()

wait_for_completion()

report(“final”)

report(“timeout”)

Createtopobjects

Build andconfigure

Maintestrun

Timeoutpath

Testresults

The Dance

Source: Hardware Verification with C++, page 97

your_test::new(testbench*, watchdog*, std::string)

testbench::new(std::string)

verification_top()

your_test::randomize()

testbench::randomize()

watchdog::time_zero_setup()

testbench::time_zero_setup()

your_test::time_zero_setup()

watchdog::out_of_reset()

testbench::out_of_reset ()

your_test::out_of_reset()

watchdog::write_to_hardware()

testbench::write_to_hardware()

your_test::write_to_hardware()

watchdog::start()

testbench::start()

$TRUSS_HOME/src/watchdog.cpp

your_test::start()

your_test::wait_for_completion()

testbench::wait_for_completion()

your_test::report(“Final Report”)

testbench::report(“Final Report”)

$PROJECT_HOME/verification/tests/your_test.cpp

$PROJECT_HOME/verification/testbench/top/testbench.cpp

Hold the reset line for the minimal amount, then release it. Return when registers can be accessed

Pull wires/registers up or down before releasing the reset line

Perform top-level randomization, for example, chose interfaces or features to be tested

testbench

Legend

your_test

watchdog

watchdog::new(std::string)Build objects,apply constraints

Push the configurations down to the hardware

Pause until the checkers are finished

Print which components have completed

Exercise the chip

The Dance – Detailed Flow

Source: Hardware Verification with C++, page 117

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The “Dance” ̶ painfully detailedyour::new(generator, bfm, checker)

your::randomize()

your::time_zero_setup()

your::out_of_reset()

your::write_to_hardware()

test_component::start()

your::generate_()

test_component:wait_for_completion()

test_component::final_report (“Final Report”)

Start your generator, BFM, and checker

Performs the same function as the top-level components

Set up and run your“main traffic” method

Wait for your checker to complete

test_component::start_()

your::start_components_()

test_component::run_component_traffic_()

$PROJECT_HOME/verification/test_components/your_test_component.cpp

your_test_component:wait_for_completion_ ()

$TRUSS_HOME/inc/truss_test_component.h

called from the same named method in test

Test Component Dance – Detailed Flow

base implementation provided

you must implement

Your test

The test buildsyour test component

Legend

your_test_component::randomize()

test_component::start()

your_test_component::generate_()

Start your testbench generator, bfm, checker

Start_ runs in a thread!

Set up and run your “main traffic” method

test_component::start_()

your_test_component::start_components_()

test_component::run_component_traffic_()

The irritator dance

irritator::run_component_traffic_()

your_test_component::inter_generate_gap_() Pause the generate loop

from your_test::start()

until irritator::stop_generation()

$PROJECT_HOME/verification/test_components/your_irritator.cpp

$TRUSS_HOME/inc/test_component.h, and irritator.hyou may implement

you must implement

Legend

Source: Hardware Verification with C++, page 120 Source: Hardware Verification with C++, page 121

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Summary• OOP is a little bit of syntax with a large

amount of attitude.

• Learning OOP is gradual process, with making mistakes an integral part.

• OOP is not really that “different” – just different packaging

• See www.trusster.com for forums, articles, code, and more.

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Q & A*

*shameless plug