Optimization of Verification Effort
using
Reusable Sequence Collection
Dipesh Handa
Gaurav Chugh
Gaurav Minda
Kumar Rajeev Ranjan
Authors
 Dipesh Handa :
R & D Engineer
+91-11-49233970
dhanda@synopsys.com
 Gaurav Minda
 Gaurav Chugh
Manager CAE
+91-11-49233980
cgaurav@synopsys.com
 Kumar Rajeev Ranjan
CAE
+91-11-49233952
gminda@synopsys.com
CAE
+91-11-49233955
kranjan@synopsys.com
Agenda
• Introduction
 Reusable sequence collection
 Guidelines to develop reusable sequences
• Use model
• Benefits
Reusable Sequence Collection
• It is a set of configurable sequences with different level of complexities.
• Depending on requirement, user can use different level of sequences.
• Different levels can be –
Level 0 - Sequences to model functionality check for
basic operations
Level 1 - Sequences to model functionality check for
basic scenarios
Level 2 - Sequences to model functionality check for
complex scenarios
•
Level 2
Level 1
Sequence collection should be implemented in layered architecture Level 0
NOTE : Levels may increase as per requirement of complexity.
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Guidelines : Reusable Sequence Collection
 Sequence collection should be implemented in layered architecture
Level 1 sequences will use Level 0 sequences and
Level 2 sequences will use level 1 sequences and so on
 Level 0 sequences : Model basic scenarios like Single READ, Single WRITE.
 Identify configurable properties of transaction class and declare them
as local properties
 Configuration mechanism to get value of local properties and assign the
local properties to transaction properties
 Level 1 sequences : Model intermediate scenarios like READ followed by WRITE.
 Declare local properties in Level 1 sequence to map with the Level 0
sequence properties
 Configuration mechanism to get value of local properties and assign the
local properties to sequence 0 properties
Better Understanding of Implementation and Guidelines
Clock
MASTER
data
SLAVE
Scenario : Multiple number of Write -> Read operation between Master and Slave
Master transaction class :
Class master_transaction extends uvm_transaction;
Commonly used in all scenarios
rand bit [7:0] address = 8’h01;
rand bit [7:0] data = 8’h00;
rand bit [1:0] command;
Constraints to provide control on range
bit enable;
bit reset;
constraint valid_cmd { command inside {READ, WRITE}; }
constraint valid_data {data inside {[8’h00:8’hff]};}
constraint valid_addr {address inside {[8‘h00, 8’h04]};}
endclass : master_transaction
Out of 5 properties only 2 properties (address and data) can be reused.
Level 0 Sequence for Write and Read transfer
Declaration and initialization of Local
Class wr/rd_seq_level0 extends uvm_sequence #(master_transaction)
properties of random type
rand bit [7:0] address = 8’h01;
rand bit [7:0] data = 8’h00;
constraint valid_range {address inside {[8’h00: 8’h04]}} // controlled value of local
variables
-----------------------Apply constraint on
-----------------------local properties
virtual task body();
// getting values in local variables from test case level
uvm_config_db#(bit[7:0]) :: get (null, get_full_name(),”address” , address);
uvm_config_db#(bit[7:0]) :: get (null, get_full_name(),”data” , UVM
data);Configuration setting
to get value from test case
`uvm_do_with(req, { req.address == address;
level
req.data == data;
req.command == WRITE/READ;
}) // Write transaction
Applying local properties as
endtask: body
constraints to generate transaction
endclass : wr_seq_level0
Level 1 Sequence for multiple Write-Read transaction
Class wr_rd_seq_level1 extends uvm_sequence #(master_transaction)
rand int unsigned count = 1;
rand bit [7:0] address = 8’h01;
Local properties of level 1 sequence
rand bit [7:0] data = 8’h00;
constraint valid_range (address inside {[8’h00: 8’h04]};
count inside {[0:10]}; )
// controlled value of local variables
-----------------------wr_seq_level1 wr;
// handle of Level 0 write sequence
Handles of level 0
rd_seq_level1 rd;
// handle of Level 0 read sequence
sequences
-----------------------virtual task body();
// getting values in local variables from higher level
Configuration
uvm_config_db#(bit[7:0]) :: get (null, get_full_name(),”address” , address);
mechanism to get
uvm_config_db#(bit[7:0]) :: get (null, get_full_name(),”data” , data);
the value from test
uvm_config_db#(int unsigned) :: get (null, get_full_name(),”count” , count);
case
for(int i =0; i<count; i++) // no. of iteration
Applying local properties as
begin
constraints to generate transaction
`uvm_do_with(wr, { wr.address == address;
wr.data == data; }) // Write transaction
`uvm_do_with(rd, { rd.address == address;}) // Read transaction
end
endtask: body
Count to generate multiple
endclass: wr_rd_seq_level1
transaction
Test to provide configuration information to sequence
Class seq_test extends uvm_test;
---------------------------------------------virtual function void build_phase(uvm_phase phase);
Configuration setting to set default
sequence on manster sequencer
// Apply the master sequence to the master sequencer
uvm_config_db#(uvm_object_wrapper)::set(this,"env.master.sequencer.main_phase", "default_sequence",
wr_rd_seq_level1 ::type_id::get());
// Apply directed values to local variables of sequence
uvm_config_db#(int unsigned)::set(this,"env.master.sequencer.wr_rd_seq_level1",“count", 2);
uvm_config_db#(bit [7:0])::set(this, "env.master.sequencer.wr_rd_seq_level1",“address", 8‘h02);
uvm_config_db#(bit [7:0])::set(this,"env.master.sequencer.wr_rd_seq_level1",“data", 8’hff);
endfunction: build_phase
endclass: seq_test
Configuration setting to pass
directed value to sequence
properties
Captured Configurable Fields from various protocols
MIPI CSI2
AXI
Id
Address
Burst_length
Burst_size
Burst_type
Cmd_type
Data
Write_strob etc.
UART
count_packet
rts_delay
cts_delay
delay_packets
payload etc.
Virtual_channel_id
Num_data_lines
Num_embedded_lines
Num_data_pixels
Num_embedded_pixels
Num_frames etc.
Benefits
 It optimizes the verification process by reducing
 Number of sequences
 Time span
 Manual Efforts
 Engineering Cost
• Comparative Study
In Terms of
With Reusability
Without Reusability
Number of Test &
Sequences required
~5 Reusable Sequences
~30 Normal Directed
Sequences
Abstract
As a result of increasing complexity of Designs, majority of verification
effort goes into stimulus pattern generation by writing UVM/OVM
sequences and tests. Sometimes there is no reuse across common type
of sequences which results in code duplication and verification closure
time is on higher side
This paper showcases the concept of building reusable UVM/OVM
sequences which can be used to generate different stimulus patterns
by configuring the reusable sequences. Reusability reduces code
verification efforts and verification closure time. Code snippet of
sample reusable sequences are shown to help verification engineers to
apply the same concepts while building the reusable sequences for
different protocols like AMBA, UART, MIPI