Optimization of Verification Effort using Reusable Sequence Collection Dipesh Handa Gaurav Chugh Gaurav Minda Kumar Rajeev Ranjan

Authors Dipesh Handa : R & D Engineer Gaurav Chugh Manager CAE Gaurav Minda CAE Kumar Rajeev Ranjan CAE

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 Sequence collection should be implemented in layered architecture NOTE : Levels may increase as per requirement of complexity. Level 2 Level 1 Level 0 COMPLEXITYCOMPLEXITY

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 Scenario : Multiple number of Write -> Read operation between Master and Slave Master transaction class : MASTERSLAVE Clock data Class master_transaction extends uvm_transaction; rand bit [7:0] address = 8’h01; rand bit [7:0] data = 8’h00; rand bit [1:0] command; 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. Commonly used in all scenarios Constraints to provide control on range

Class wr/rd_seq_level0 extends uvm_sequence #(master_transaction) 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 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”, data); `uvm_do_with(req, { req.address == address; req.data == data; req.command == WRITE/READ; }) // Write transaction endtask: body endclass : wr_seq_level0 Level 0 Sequence for Write and Read transfer Declaration and initialization of Local properties of random type Apply constraint on local properties UVM Configuration setting to get value from test case level Applying local properties as constraints to generate transaction

Class wr_rd_seq_level1 extends uvm_sequence #(master_transaction) rand int unsigned count = 1; rand bit [7:0] address = 8’h01; 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 rd_seq_level1 rd; // handle of Level 0 read sequence virtual task body(); // getting values in local variables from higher 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”, data); uvm_config_db#(int unsigned) :: get (null, get_full_name(),”count”, count); for(int i =0; i<count; i++) // no. of iteration begin `uvm_do_with(wr, { wr.address == address; wr.data == data; }) // Write transaction `uvm_do_with(rd, { rd.address == address;}) // Read transaction end endtask: body endclass: wr_rd_seq_level1 Level 1 Sequence for multiple Write-Read transaction Local properties of level 1 sequence Handles of level 0 sequences Configuration mechanism to get the value from test case Applying local properties as constraints to generate transaction Count to generate multiple transaction

Class seq_test extends uvm_test; virtual function void build_phase(uvm_phase phase); // 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 Test to provide configuration information to sequence Configuration setting to set default sequence on manster sequencer Configuration setting to pass directed value to sequence properties

Captured Configurable Fields from various protocols AXI UART  Id  Address  Burst_length  Burst_size  Burst_type  Cmd_type  Data  Write_strob etc.  count_packet  rts_delay  cts_delay  delay_packets  payload etc. MIPI CSI2  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 In Terms ofWith ReusabilityWithout Reusability Number of Test & Sequences required ~5 Reusable Sequences~30 Normal Directed Sequences Comparative Study

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