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naikur.gohil

Status UVM_HAS_X is not reported when register value is X

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In uvm_reg_map::do_bus_read() task, after the call to adapter.bus2reg() function, do_bus_read() function checks for any Xs in data field.

 

Code from uvm_reg_map:

 

      uvm_reg_bus_op rw_access;
      uvm_reg_data_logic_t data;
 
      data = rw_access.data & ((1<<bus_width*8)-1);
 
      rw.status = rw_access.status;
 
      if (rw.status == UVM_IS_OK && (^data) === 1'bx)
        rw.status = UVM_HAS_X;
 
Here, rw_access.data is of type "bit" and is assigned to data which is of type "logic". and then data is checked for Xs. But, as rw_access.data is "bit" type, it will never contain Xs or Zs.
As a result, data will never have Xs, so rw.status will not set to UVM_HAS_X. So even if bus2reg function samples Xs from the bus, those Xs never make upto tasks in uvm_reg_map class.
 
Some supporting code::
uvm_reg_defines.svh: `define UVM_REG_DATA_TYPE bit
uvm_reg_model.svh  :  typedef `UVM_REG_DATA_TYPE unsigned [`UVM_REG_DATA_WIDTH-1:0]  uvm_reg_data_t ;
uvm_reg_item.svh: 
typedef struct {
  uvm_access_e kind;
  uvm_reg_addr_t addr;
  uvm_reg_data_t data;
  int n_bits;
  uvm_reg_byte_en_t byte_en;
  uvm_status_e status;
} uvm_reg_bus_op;

 

 
In my testbench, I want uvm_reg_map to set the status to UVM_HAS_X whenever data received for a register read transaction from DUT is X. How do I achieve that?

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hi,

 

your adapter.bus2reg() should set rw_access.status to UVM_HAS_X when bus_op.data contains X values in relevant positions. the two lines

 

if (rw.status == UVM_IS_OK && (^data) === 1'bx)

>        rw.status = UVM_HAS_X;
 
seem bogus.
 
/uwe

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