18 UVM Scoreboard-编程知识

UVM scoreboard是一个检查DUT功能的组件。它用analysis export从monitor接受transaction事务以进行检查。

uvm_scoreboard class declaration:

virtual class uvm_scoreboard extends uvm_component

User-defined scoreboard class declaration:

用户定义的scoreboard是从 uvm_scoreboard 扩展而来的，而 uvm_scoreboard 又派生自 uvm_component。

class <scoreboard_name> extends uvm_scoreboard;

1 uvm_scoreboard class hierarchy

3 Scoreboard Usage

使用analysis export从monitor接收transaction以进行检查。
scoreboard有一个参考模型reference model可以与design行为进行比较。reference model也称为预测器predictor，它实现design行为，以便scoreboard可以将 DUT 结果与相同驱动刺激的参考模型reference model结果进行比较。

3 How to write scoreboard code in UVM?

创建一个从 uvm_scoreboard 扩展的用户定义的scoreboard类，并将其注册到工厂中。
声明analysis export以从monitor接收sequence item或transaction。
编写标准 new() 函数。由于记分板是一个 uvm_component。new() 函数有两个参数：字符串名称name和 uvm_component 父类parent。
实现 build_phase 并创建 TLM analysis export实例。
实现一个 write 方法来接收来自monitor的事务。
实现run_phase 以在整个仿真时间内检查 DUT 功能。

3.1 Scoreboard Example

class scoreboard extends uvm_scoreboard;uvm_analysis_imp #(seq_item, scoreboard) item_collect_export;seq_item item_q[$];`uvm_component_utils(scoreboard)function new(string name = "scoreboard", uvm_component parent = null);super.new(name, parent);item_collect_export = new("item_collect_export", this);endfunctionfunction void build_phase(uvm_phase phase);super.build_phase(phase);endfunctionfunction void write(seq_item req);`uvm_info(get_type_name, $sformatf("Received transaction = %s", req), UVM_LOW);item_q.push_back(req);endfunctiontask run_phase (uvm_phase phase);seq_item sb_item;forever beginwait(item_q.size > 0);if(item_q.size > 0) beginsb_item = item_q.pop_front();// Checking comparing logic...        endendendtask
endclass

4 UVM Scoreboad types

根据设计功能，记分板可以通过两种方式实现。

in-order scoreboard
out-of-order scoreboard

4.1 In-order scoreboard

有序记分板（in-order scoreboard）对于输出顺序与stimuli激励相同的设计很有用。比较器将以相同的顺序比较预期输出流和实际输出流。他们将独立抵达。因此，评估必须阻塞，直到预期transaction和实际transaction都存在。

要实现此类scoreboard，更简单的方法是实现 TLM analysis FIFO。有关更多详细信息，请访问TLM analysis FIFO部分。在下面的示例中，有两个monitor，其分析端口连接到记分板以提供输入和输出事务。

class inorder_sb extends uvm_scoreboard;`uvm_component_utils(inorder_sb)uvm_analysis_export #(txn) in_export, out_export;uvm_tlm_analysis_fifo #(txn) in_fifo, out_fifo;function new (string name = "inorder_sb" , uvm_component parent = null) ;super.new(name, parent);endfunctionfunction void build_phase (uvm_phase phase);in_fifo    = new("in_fifo", this);out_fifo   = new("out_fifo", this);in_export  = new("in_export", this);out_export = new("out_export", this);endfunctionfunction void connect_phase (uvm_phase phase);in_export.connect(in_fifo.analysis_export);out_export.connect(out_fifo.analysis_export);endfunctiontask run_phase( uvm_phase phase);txn in_txn;txn exp_txn, act_txn;forever beginin_fifo.get(in_txn);process_data(in_txn, exp_txn); out_fifo.get(act_txn);if (!exp_txn.compare(act_txn)) begin`uvm_error(get_full_name(), $sformat("%s does not match %s", exp_txn.sprint(), act_txn.sprint()), UVM_LOW);endendendtask// Reference model task process_data(input txn in_txn, output txn exp_txn);// Generate expected txn for driven stimulus......endtask
endclass

4.2 Out-of-order scoreboard

无序记分板out-of-order scoreboard对于输出顺序与驱动输入激励stimuli不同的设计很有用。基于输入激励参考模型将生成 DUT 的预期结果，并且实际输出预计以任何顺序出现。因此，需要存储从输入激励生成的此类不匹配事务，直到从待比较的 DUT 接收到相应的输出为止。为了存储此类事务，关联数组被广泛使用。根据索引值，transactions存储在预期和实际关联数组中。当匹配的数组索引发生比较时，关联数组中的条目将被删除。

class txn extends uvm_sequence_item;int id;  // other class properties//...
endclassclass out_of_order_sb extends uvm_scoreboard;`uvm_component_utils(out_of_order_sb)uvm_analysis_export #(txn) in_export, out_export;uvm_tlm_analysis_fifo #(txn) in_fifo, out_fifo;// associative array of class type as txn and indexed by inttxn expected_out_array[int];txn actual_out_array[int];// Store idx in separate queues.int expected_out_q[$], actaul_out_q[$];function new (string name = "out_of_order_sb" , uvm_component parent = null) ;super.new(name, parent);endfunctionfunction void build_phase (uvm_phase phase);in_fifo    = new("in_fifo", this);out_fifo   = new("out_fifo", this);in_export  = new("in_export", this);out_export = new("out_export", this);endfunctionfunction void connect_phase (uvm_phase phase);in_export.connect(in_fifo.analysis_export);out_export.connect(out_fifo.analysis_export);endfunctiontask run_phase( uvm_phase phase);txn in_txn, out_txn;forever beginfork      begin in_fifo.get(in_txn);process_data(in_txn);endbeginout_fifo.get(out_txn);actual_out_array[out_txn.id] = out_txn;actaul_out_q.push_back(out_txn.id);endjoincompare_data();endendtask// check_phase to check whether any entry is pending in queues.function void check_phase(uvm_phase phase);super. check_phase(phase);if(expected_out_q.size() != 0) `uvm_info (get_full_name(), $sformatf("expected_out_q size = %0d", expected_out_q.size()), UVM_LOW);if(actaul_out_q.size() != 0) `uvm_info (get_full_name(), $sformatf("actaul_out_q size = %0d", actaul_out_q.size()), UVM_LOW);endfunctiontask process_data(txn in_txn);txn exp_out_txn;// Using reference models, generate output for input stimulus.// store expected output (exp_out_txn) in expected_out_array......expected_out_array[in_txn.id] = exp_out_txn;expected_out_q.push_back(in_txn.id);endtasktask compare_data();int idx;txn exp_txn, act_txn;if(expected_out_q.size() > && actaul_out_q.size() > 0) beginidx = expected_out_q.pop_front();// Look for idx in actual_out_array to see whether the output has been received for a driven stimulus or not.if(actual_out_array.exists(idx)) begin exp_txn = expected_out_array[idx];act_txn = actual_out_array[idx];if(!exp_txn.compare(act_txn)) begin`uvm_error(get_full_name(), $sformat("%s does not match %s", exp_txn.sprint(), act_txn.sprint()), UVM_LOW);endelse beginexpected_out_array.delete(idx);actual_out_array.delete(idx);endendelse expected_out_q.push_back(idx); // exp_idx is not found in actual_out_array.endendtask
endclass