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Sequence, Sequence on the Wall, Who’s the Fairest of Them

Sequence, Sequence on the Wall, Who’s the Fairest of Them A ll? Using SystemVerilog UVM Sequences for Fun and Profit by Rich Edelman and Raghu Ardeishar Verification Technologists Mentor Graphics Questa Verification Platform

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Sequence, Sequence on the Wall, Who’s the Fairest of Them






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Sequence, Sequence on the Wall, Who’s the Fairest of Them All?Using SystemVerilog UVM Sequences for Fun and Profit byRich Edelman and Raghu ArdeisharVerification TechnologistsMentor Graphics Questa Verification Platform

thefreedictionary.com/fairest Who’s the fairest? fair 1  (fâr)adj. fair·er, fair·est 1 . Of pleasing appearance, especially because of a pure or fresh quality; comely.2. a. Light in color, especially blond: fair hair.b. Of light complexion: fair skin. 3. Free of clouds or storms; clear and sunny: fair skies. 4. Free of blemishes or stains; clean and pure: one's fair name.5. Promising; likely: We're in a fair way to succeed.6. a. Having or exhibiting a disposition that is free of favoritism or bias; impartial: a fair mediator.b. Just to all parties; equitable: a compromise that is fair to both factions.7. Being in accordance with relative merit or significance: She wanted to receive her fair share of the proceeds.8. Consistent with rules, logic, or ethics: a fair tactic.9. Moderately good; acceptable or satisfactory: gave only a fair performance of the play; in fair health. 10. Superficially true or appealing; specious: Don't trust his fair promises. 11. Lawful to hunt or attack: fair game.12. Archaic Free of all obstacles.

Overview - Smorgasbord UVM ReviewAgentsTransactions SequencesDriversSequence APIstart_item finish_itemstartgrab priorityHierarchy/Constraints Dice/rollWords/SentenceSpecial SequencesTask interfaceCommand line (+SEQ=seqA)Reading from a fileC codeOut-of-Order

Agent manages an interfaceDriver wiggles the pinsMonitor monitors pin wigglesSequencer arbitrates access to the driver Sequence generates transactions and sends them to the driver AGENT Agents DRVR MON SQR trans trans SEQ SEQ SEQ SEQ SEQ SEQ Interface : Pins & Pin Wiggles

Fun Sequence/Sequencer/DriverThe sequence, sequencer and driver communicate one transaction at a time with each other. The sequence creates (constructs) a transaction and sends it to the driver.The sequencer arbitrates amongst multiple sequencesFinally the driver gets the transaction and acts on it AGENT DRVR SQR transA SEQA SEQC SEQB 1 2 3

Transactions – here’s threeTransaction as a payload class trans_c extends uvm_sequence_item ; `uvm_object_utils(trans_c) rand bit rw ; rand bit[31: 0] addr; rand bit [ 31 : 0 ] data ; endclass typedef enum { DICE1 = 1 , DICE2, DICE3 , DICE4, DICE5 , DICE6} dice_t;class dice_item extends uvm_sequence_item; `uvm_object_utils(dice_item) rand dice_t value; ... endclass class packet extends uvm_sequence_item ; `uvm_object_utils( packet ) rand bit [ 7 : 0 ] som ; rand bit [ 7 : 0 ] addr ; rand bit [ 7 : 0 ] payload [ 8 ]; bit [ 7 : 0 ] checksum ; rand bit [ 7 : 0 ] eom ; constraint val { som == ' 0 ; eom == ' 1 ; foreach ( payload [ i ]) payload [ i ] inside {[ 0 : 100 ]}; } function void post_randomize (); checksum = 0 ; foreach ( payload [ i ]) checksum = f(checksum, payload [ i ]); endfunction endclass

SequencesSequences are functors a class wrapper around a body() taskA sequence can have two jobsGenerate a sequence of transactionsStart other sequences … class dice_item extends uvm_sequence_item; rand dice_t value ; ...endclass class roll_sequence extends uvm_sequence#(dice_item); rand int how_many ; task body (); dice_item t ; for (int i = 0; i < how_many; i++) begin t = dice_item::type_id::create(...); if (!t.randomize ()) begin `uvm_fatal("SEQ" , "Randomize failed") end start_item(t); finish_item(t ); end endtask endclass AGENT DRVR SQR SEQA SEQC SEQB c reate r andomize s tart_item f inish_item

Sequences – “virtual sequences”Start other sequences class axx_basic_sequence extends uvm_sequence_base; `uvm_object_utils(axx_basic_sequence) axx_env env; task body(); abc_sequence seq1; xyz_sequence seq2 , seq3; seq1 = abc_sequence :: type_id :: create ( "seq1" ); seq2 = xyz_sequence :: type_id :: create ( "seq2"); seq3 = xyz_sequence::type_id ::create("seq3"); fork seq1.start(env.agent1.sequencer ); seq2.start(env.agent2.sequencer); seq3. start(env.agent3.sequencer ); join endtaskendclass

Sequences with grabGet exclusive use of the sequencer class roll_sequence extends uvm_sequence #(dice_item); `uvm_object_utils(roll_sequence) rand int how_many; constraint val { how_many > 70 ; how_many < 100 ; } task body (); dice_item t ; grab (); for ( int i = 0; i < how_many; i++) begin t = dice_item::type_id::create($sformatf( "t%0d", i)); if (!t.randomize()) begin `uvm_fatal("SEQ", "Randomize failed") end start_item (t); finish_item (t); end ungrab (); endtask endclass AGENT DRVR SQR SEQA SEQC SEQB

Transactions with priorityDefault priority is 100. Higher numbers are better.Don’t forget to change the sequencer mode sqr .set_arbitration(SEQ_ARB_STRICT_FIFO ); class roll_sequence extends uvm_sequence #( dice_item); `uvm_object_utils(roll_sequence) rand int how_many ; constraint val { how_many > 70 ; how_many < 100 ; } task body(); dice_item t; for(int i = 0 ; i < how_many ; i++) begin t = dice_item::type_id::create($sformatf( "t%0d", i)); if (!t.randomize ()) begin `uvm_fatal("SEQ" , "Randomize failed") end start_item(t, 1000); finish_item ( t ); end endtask endclass AGENT DRVR SQR SEQA SEQC SEQB

DriverDriver handshake with the sequence class driver extends uvm_driver#(dice_item); `uvm_component_utils(driver) // Simple counter for each face seen int distribution [dice_t]; task run_phase(uvm_phase phase ); forever begin dice_item t; seq_item_port . get_next_item ( t ); distribution [ t . value ]++; `uvm_info( "DRVR" , $sformatf(" Got %s [%p]", t.convert2string (), distribution), UVM_MEDIUM ) // Send to BUS... seq_item_port .item_done(); end endtask endclass AGENT DRVR SQR SEQA SEQC SEQB

Tasks Wrapping SequencesSequence wrapped with a simple task Task does ‘seq.start(sequencer)’ task read( input bit [7:0] addr , output bit [7:0 ] data); read_seq seq ; seq = read_seq:: type_id :: create ( "read" ,, get_full_name ()); seq . addr = addr ; seq. start(seqr); data = seq.data; endtask class trans extends uvm_sequence_item ; `uvm_object_utils(trans) rand bit rw; rand bit [7:0 ] addr; rand bit [7:0 ] data; ...endclass class read_seq extends uvm_sequence #( trans ); `uvm_object_utils( read_seq ) rand bit [ 7 : 0 ] addr ; // Input bit [ 7 : 0 ] data ; // Output task body (); trans t ; t = trans:: type_id::create("t",, get_full_name()); t. rw = 1; t . addr = addr ; start_item ( t ); finish_item ( t ); data = t . data ; endtask endclass

Command line - +SEQ=<seqA> task run_phase(uvm_phase phase ); string sequence_name; uvm_object obj; simple_value_base_class seq ; string list_of_sequences[$]; uvm_cmdline_processor clp; clp = uvm_cmdline_processor::get_inst (); clp . get_arg_values ( "+SEQ=" , list_of_sequences ) foreach ( list_of_sequences [ n ]) begin sequence_name = list_of_sequences[ n]; phase .raise_objection(this); obj = factory.create_object_by_name( sequence_name); if ( obj == null) /* Handle Error */ if (!$cast(seq , obj)) /* Handle Error */ seq.env = env; seq.start ( null ); phase . drop_objection ( this ); end endtask <SIM> +SEQ= seqA +SEQ= seqB

Reading from a file - +FILE=<file> class read_sequence_from_file extends uvm_sequence #( value_item); `uvm_object_utils(read_sequence_from_file) task body (); int fd, count ; string filenames[$], sequence_name; uvm_object obj; simple_value_base_class seq ; uvm_cmdline_processor clp ; clp = uvm_cmdline_processor :: get_inst (); clp . get_arg_values ( "+FILE=", filenames ) foreach (filenames[ n]) begin fd = $fopen(filenames[n], "r"); while(!$feof(fd)) begin ret = $fscanf(fd , "%s %d", sequence_name , count); obj = factory.create_object_by_name(sequence_name ); if (obj == null ) /* Handle Error */ if (!$cast( seq , obj )) /* Handle Error */ if (! seq . randomize () with { seq . how_many == count ;}) /* Handle Error */ seq . start ( m_sequencer ); end // while end // foreach endtask endclass sequences.txt:fibonacci_sequence 10triangle_sequence 20 <SIM> +FILE=sequences.txt +FILE=sequences2.txt

DPI-C (bound)Use C code to Get stimulus inputGet expected outputScoreboard (checker) interface my_interface (); import "DPI-C" context task c_calc ( output int x ); export "DPI-C" task intf_calling_back; seq my_class_handle; function void init(seq s ); s . vif = interface :: self (); my_class_handle = s; endfunction task intf_calling_back(output int x); my_class_handle.class_calling_back(x ); endtaskendinterface class seq; virtual my_interface vif; task class_calling_back(output int x); # 10 x = id; endtask task body (); int x ; for ( int i = 0 ; i < 5 ; i ++) vif . c_calc ( x ); endtask endclass C Code int c_calc( int *val) { int id; intf_calling_back (&id); printf ( "c_calc() Scope = %s\n ", svGetNameFromScope(svGetScope())); *val = id++; return 0 ; } 1 2 3 4

DRIVER Out-of-Order – sequence/driver SEQUENCE forever begin get_next_item(t); work_list.push (t); item_done();end forever begin work_list.pop(t); t.item_really_started(); lookup[tag] = t; send t to BUS end Execute forever begin @(interrupt); t = lookup[tag]; t.resp = BUS.resp ; resp_list.push(t); end ISR forever begin resp_list.pop(t); t.item_really_done();end RSP trans t; t = new (“t”); start_item(t); finish_item(t); Run DUT t

Out-of-Order – item_really_done SEQ trans t; t = new(“t”);start_item(t);finish_item(t); class trans ... bit item_really_done_e; function item_really_done(); item_really_done_e = 1; endfunction ... endclass t DRIVER forever begin get_next_item(t); work_list.push (t); item_done(); end forever begin resp_list.pop (t); t.item_really_done(); end RSP Run class my_sequence_base ... function finish_item(trans t); super .finish_item(t); wait( t.item_really_done_e == 1); endfunction

SummarySequences are the way to write tests. Just code that ...Starts other sequencesSends transactionsSequences have an APIRandomized tests – constraints, layeringDirected tests, C code, files, command line Building collections of sequences is a good ideaGlad to share source code. Some of it is in the paper. Questions? rich_edelman@mentor.com

BACKUP SLIDES

Fun with WordsEncryption hardware – one word at a time Job of the StimulusGenerating wordsGenerating four-letter-wordsSentences, Paragraphs, Chapters, …Use Constraints Unique combinationsDistribution of lettersReally  Fun with Constraints SV LRM Chapter 18 – only(!) 50 pages out of 1315 DUT word mode e ncrypted word Hold the Presses! News Flash Just released

Transaction/Sequence Design Transaction: a word (data), an encryption mode and the result (secret_data)Sequence: create a word and send it. virtual class my_sequence extends uvm_sequence#(transaction); `uvm_object_utils(my_sequence) rand byte data[]; task body(); transaction t; t = transaction::type_id::create("t"); start_item(t); if (!t.randomize()) `uvm_fatal("MSG", "Randomization failed") t.data = data; finish_item(t); `uvm_info("MSG", $sformatf("secret=%s", t.secret_data ), UVM_MEDIUM) endtaskendclass class transaction extends uvm_sequence_item ; ... rand mode_t mode; // CLR or ROT13 rand byte data[]; string secret_data;endclass

Four Letter Words - constraintsInheritance Sequence: Extends ‘my_sequence’. “IS-A”Randc data from the gadget ‘r’.pre_randomize()post_randomize()What is ‘r’? class four_letter_words extends my_sequence; `uvm_object_utils(four_letter_words) four_letter_words_randc r; function new(string name = “..."); super.new(name); r = new(); endfunction function void pre_randomize(); if (!(r.randomize())) `uvm_fatal(...) endfunction function void post_randomize(); data = r.sdata ; endfunction endclass

The Gadget ‘r’ Just a container which allows for randc to be used.How to generate all the possible four letter words with no repeats?Randomize ‘value’ Convert ‘value’ to string sdata Modulo 26 operations class four_letter_words_randc; string sdata; randc int value; constraint val { value >= 0; value < 456976; } function void post_randomize(); int v; sdata = " "; v = value; for(int i = 0; i < 4; i++) begin sdata [ i ] = (v%26) + "a"; v = v/26; end endfunction Note to math people 26**4 = 456976

Short WordMore… InheritanceConstraints class short_word_seq extends my_sequence; `uvm_object_utils(short_word_seq) rand int length; constraint val_length { length >= 3; length <= 8; } constraint val_data_length { data.size() == length; } constraint val_data { foreach (data[ i]) { data[i] inside {["a":"z"]}; // 'a' to 'z' if ( i == 0) // First letter of the word data[i] dist {" a" := 116 , ... "z" := 01}; else data[ i ] dist {" a" := 81, ... "z" := 01}; } }endclass class my_sequence extends ... `uvm_object_utils(my_sequence) rand byte data[]; task body(); transaction t; t = transaction::type_id::create("t"); start_item(t); if (!t.randomize()) `uvm_fatal(...) t.data = data; finish_item(t); endtask endclass

Sentence SeqSentence “HAS-A” seq it generates sequences and starts them.4 letterShort wordParagraphChapterBook class sentence_seq extends uvm_sequence#(transaction); `uvm_object_utils(sentence_seq) rand int how_many; rand bit use_four_letter_word = 0; constraint val_how_many {how_many > 0; how_many < 200;} task body(); uvm_sequence_base seq; for(int i = 0; i < how_many; i ++) begin if (use_four_letter_word) seq = four_letter_words::type_id::create(“..."); else seq = short_word_seq::type_id::create(“..."); if (!seq.randomize()) `uvm_fatal("SEQ", "Randomize failed") seq.start(m_sequencer); end endtask

Factory - OverridesType based override Instance based override class test extends uvm_test; `uvm_component_utils(test) task run_phase(uvm_phase phase); n_packets seq1, seq2; phase.raise_objection(this); packet::type_id::set_type_override( packet_with_randc_addr::get_type); packet::type_id::set_inst_override( big_packet::get_type(), "uvm_test_top.e1.sequencer.seq1.packet"); seq1=n_packets::type_id::create("seq1",,get_full_name()); seq2=n_packets::type_id::create("seq2",,get_full_name()); factory.print();...