UVM RAL: Randomizing registers in a register model
-
22-12-2019 - |
Question
I have a large register map modelled with RAL and I would like to randomize some of the registers. If I want to constrain the registers seperately then this is simple:
reg_model.register_a.randomize() with {value > 5;}
reg_model.register_b.randomize() with {value < 2;}
reg_model.update(status);
However, if I want a relationship between the two values written I think I have to add a constraint to the whole register model:
reg_model.randomize() with {register_a.value > register_b.value;}
reg_model.register_a.update(status);
reg_model.register_b.update(status);
The problem here is that the other 254 registers in the model will also get randomized. I could just update the two registers that I want randomized, but then the mirror will not match the hardware. If I had backdoor access working I could refresh the mirror, but I don't and I certainly don't want to read back 254 registers through the front door.
Is there a way to randomize just those two registers yet still have the constraint solver maintain a relationship between them?
Solution
You could do
reg_model.randomize(register_a,register_b) with {register_a.value > register_b.value;}
Then only registers a and b will get randomized.
OTHER TIPS
This can't possibly work because registers don't have a "value" variable, only fields have the "value" member variable.
This should work:
reg_model.randomize(register_a,register_b) with {register_a.get() > register_b.get();}
Here my two cents, Here all registers and all fields are constrained to zero.
top_regm.get_registers(regs, UVM_HIER); //NOW take ALL registers (regs) inside the block
regs.sort with (item.get_address()); //sort ascending by address
for (int unsigned r=0; r<regs.size(); r++) begin
assert(regs[r].randomize with {
regs[r].get() == 0; //constraint with function is heavy consumming
} );
reg_value_q.push_back(regs[r].get()); //store all the constrained values in a queue
end