SystemVerilog looping through hierarchy

Question

I have registers instantiated in a Register block Regblock as such:

DUT.Regblock.Register1
DUT.Regblock.RegisterA
DUT.Regblock.RegisterABC
...

All these registers have the same inner structure. I would like to simulate the effects of bit flips in these registers.

//Here an attempt to do bit flips
bitFlipLocation = $random;
force  DUT.RegBlock.Register1.reg[bitFlipLocation] = ~DUT.RegBlock.Register1.reg[bitFlipLocation];
release DUT.ABCStar1.RegBlock.Register1.reg[bitFlipLocation];

Is there a way to create a loop over all DUT.Regblock.Register1, RegisterA, RegisterABC, ... inside RegBlock and create these bit flips?

no, there is no such way in system verilog, unless you re-declare all those variously-named registers as a some type of an array. So, but now the question is: what is the Register? is it a data struct or a module, or a block? — Serge
– Serge, Commented Aug 23, 2017 at 18:40
in this case you might want to look into arrayed instantiations and generate blocks. However, it could be a mess and the only reason to go there if you need a synthesizable model. otherwise, use Daves suggestion. — Serge
– Serge, Commented Aug 23, 2017 at 20:47

dave_59 · Accepted Answer · 2017-08-23 16:57:51Z

3

There are ways to do this, but not within the SystemVerilog language itself. You can write VPI code in C to iterate over block names and apply the forces use the C API. Or you can use tool specific commands to iterate of block names and use commands (usually Tcl) to apply the forces.

Both of those are beyond the scope of what can be shown in this forum.

answered Aug 23, 2017 at 16:57

dave_59

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4 Comments

Greg Over a year ago

Wouldn't enabling UVM and using the uvm_hdl_* methods suffice?

dave_59 Over a year ago

Yes, that is essentially the same as using the VPI. OP did not reveal if they were already using the UVM.

vrleboss Over a year ago

@dave_59 pointed me in the right direction - I am now trying to implement the solution and will post it here when I succed. I am not currently using UVM but if the implementation is simple I am interested in learning it.

Serge Over a year ago

using 'c/c++' instead of uvm functions will make it a bit more efficient though. You can do it from a dpi call. .

vrleboss · Accepted Answer · 2017-08-28 05:02:11Z

Following dave's answer I implemented the VPI code in C to loop over all register within RegBlock and randomly force bit flips at some positions (register is 32 bit wide).

#include <sv_vpi_user.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#define NULL 0

void reg_flips() {
  vpiHandle module_iter;
  vpiHandle module_obj;
  vpiHandle module_regblk;
  vpiHandle reg_nets;
  vpiHandle net;
  //Starting from the RegBlock
  module_regblk = vpi_handle_by_name("DUT.RegBlock",NULL);
  //Iterator over all register in RegBlock
  module_iter = vpi_iterate(vpiModule,module_regblk);
  while (module_iter) {
    module_obj = vpi_scan(module_iter);
    if (module_obj) {
      reg_nets = vpi_iterate(vpiReg,module_obj);
        while (reg_nets) {
          net = vpi_scan(reg_nets);
          if (net) {
            s_vpi_value val;
            val.format = vpiIntVal;
            val.value.integer = rand()%2;
            int position = rand()%32;
            //Forcing the value at a given position.
            vpi_put_value(vpi_handle_by_index(net,position),&val,NULL,vpiNoDelay);
          }
          else {
            reg_nets = NULL;
          }
        }
      }
    }
    else {
      module_iter = NULL;
    }
}

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