1. Sequence, Sequence on the Wall...
Sequence, Sequence on the Wall, Who’s the Fairest of Them All? Using SystemVerilog UVM Sequences for Fun and Profit
Questa Verification Platform by
Rich Edelman and Raghu Ardeishar
Verification Technologists
Mentor Graphics
DVCON 2013

2. thefreedictionary.com/fairest
Sequence, Sequence on the Wall...
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.
DVCON 2013

3. Overview - Smorgasbord
Sequence, Sequence on the Wall...
Overview - Smorgasbord
UVM Review
Hierarchy/Constraints
Agents
Dice/roll
Transactions
Words/Sentence
Sequences
Drivers
Special Sequences
Sequence API
Task interface
start_item
Command line (+SEQ=seqA)
finish_item
Reading from a file
start
C code
grab
Out-of-Order
priority
DVCON 2013

4. Sequence, Sequence on the Wall...
Agents
Agent manages an interface
Driver wiggles the pins
Monitor monitors pin wiggles
Sequencer arbitrates access to the driver
Sequence generates transactions and sends them to the driver
AGENT
trans
SEQ
Interface:
Pins & Pin Wiggles
MON
SQR
DRVR
trans
DVCON 2013

5. Fun Sequence/Sequencer/Driver
Sequence, Sequence on the Wall...
Fun Sequence/Sequencer/Driver
The 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 sequences
Finally the driver gets the transaction and acts on it 1
transA 3 2
SEQA
AGENT
SEQB
SQR
DRVR
SEQC
DVCON 2013

6. Transactions – here’s three
Sequence, Sequence on the Wall...
Transactions – here’s three
Transaction 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
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
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
DVCON 2013

7. Sequence, Sequence on the Wall...
AGENT
DRVR
SQR
SEQA
SEQC
SEQB
Sequences are functors
a class wrapper around a body() task
A sequence can have two jobs
Generate a sequence of transactions
Start 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);
endtask
endclass
It’s just a function call that can consume time. (An SV Task)
create
randomize
start_item
finish_item
DVCON 2013

8. Sequences – “virtual sequences”
Sequence, Sequence on the Wall...
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
endtask
endclass
It’s just a function call that can consume time. (An SV Task)
DVCON 2013

9. Sequence, Sequence on the Wall...
Sequences with grab
AGENT
DRVR
SQR
SEQA
SEQC
SEQB
Get 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);
ungrab();
endtask
endclass
DVCON 2013

10. Transactions with priority
Sequence, Sequence on the Wall...
Transactions with priority
AGENT
DRVR
SQR
SEQA
SEQC
SEQB
Default 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);
endtask
endclass
DVCON 2013

11. Sequence, Sequence on the Wall...
Driver
AGENT
DRVR
SQR
SEQA
SEQC
SEQB
Driver 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
DVCON 2013

12. Tasks Wrapping Sequences
Sequence, Sequence on the Wall...
Tasks Wrapping Sequences
Sequence 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 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
class trans extends uvm_sequence_item;
`uvm_object_utils(trans)
rand bit rw;
rand bit [7:0] addr;
rand bit [7:0] data;
...
endclass
DVCON 2013

13. Command line - +SEQ=<seqA>
Sequence, Sequence on the Wall...
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
DVCON 2013

14. Reading from a file - +FILE=<file>
Sequence, Sequence on the Wall...
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 10
triangle_sequence 20
<SIM> +FILE=sequences.txt +FILE=sequences2.txt
DVCON 2013

15. Sequence, Sequence on the Wall...
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);
endclass
DPI-C (bound)
Use C code to
Get stimulus input
Get expected output
Scoreboard (checker) 1
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);
endtask
endinterface
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; } 2 3 4
DVCON 2013

16. Out-of-Order – sequence/driver
Sequence, Sequence on the Wall...
Out-of-Order – sequence/driver
DRIVER
Run
forever begin
get_next_item(t);
work_list.push(t);
item_done();
end
Execute
SEQUENCE
forever begin
work_list.pop(t);
t.item_really_started();
lookup[tag] = t;
send t to BUS
end
trans t;
t = new(“t”);
start_item(t);
finish_item(t);
DUT
ISR t
forever begin
@(interrupt);
t = lookup[tag];
t.resp = BUS.resp;
resp_list.push(t);
end
forever begin
resp_list.pop(t);
t.item_really_done();
end
RSP
DVCON 2013

17. Out-of-Order – item_really_done
Sequence, Sequence on the Wall...
Out-of-Order – item_really_done
DRIVER
SEQ
Run
trans t;
t = new(“t”);
start_item(t);
finish_item(t);
forever begin
get_next_item(t);
work_list.push(t);
item_done();
end
class my_sequence_base ...
function finish_item(trans t);
super.finish_item(t);
wait(t.item_really_done_e == 1);
endfunction t
class trans ...
bit item_really_done_e;
function item_really_done();
item_really_done_e = 1;
endfunction
...
endclass
forever begin
resp_list.pop(t);
t.item_really_done();
end
RSP
DVCON 2013

18. Sequence, Sequence on the Wall...
Summary
Sequences are the way to write tests.
Just code that ...
Starts other sequences
Sends transactions
Sequences have an API
Randomized tests – constraints, layering
Directed tests, C code, files, command line
Building collections of sequences is a good idea
Glad to share source code. Some of it is in the paper.
Questions?
DVCON 2013

19. BACKUP SLIDES

20. Sequence, Sequence on the Wall...
Fun with Words
Encryption hardware – one word at a time
Job of the Stimulus
Generating words
Generating four-letter-words
Sentences, Paragraphs, Chapters, …
Use Constraints
Unique combinations
Distribution of letters
Really  Fun with Constraints
SV LRM Chapter 18 – only(!) 50 pages out of 1315
DUT
word
mode
encrypted word
Hold the Presses!
News Flash
Just released
DVCON 2013

21. Transaction/Sequence Design
Sequence, Sequence on the Wall...
Transaction/Sequence Design
class transaction extends
uvm_sequence_item;
...
rand mode_t mode; // CLR or ROT13
rand byte data[];
string secret_data;
endclass
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)
endtask
endclass
DVCON 2013

22. Four Letter Words - constraints
Sequence, Sequence on the Wall...
Four Letter Words - constraints
Inheritance
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(...)
function void post_randomize();
data = r.sdata;
endclass
DVCON 2013

23. Sequence, Sequence on the Wall...
The Gadget ‘r’
class four_letter_words_randc;
string sdata;
randc int value;
constraint val { value >= 0; value < ; }
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
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
Note to math people
26**4 =
DVCON 2013

24. Sequence, Sequence on the Wall...
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
Short Word
More…
Inheritance
Constraints
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
DVCON 2013

25. Sequence, Sequence on the Wall...
Sentence Seq
Sentence “HAS-A” seq
it generates sequences and starts them.
4 letter
Short word
Paragraph
Chapter
Book
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
DVCON 2013

26. Sequence, Sequence on the Wall...
Factory - Overrides
Type 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();
...
DVCON 2013