import StmtFSM :: *;

interface CRegCounter;
    method Action up(Int#(32) v);
    method Action down(Int#(32) v);
    method Action reset();
    method Int#(32) getCounter();
endinterface

module mkCounter(CRegCounter);

    Reg#(Int#(32)) ctr[4] <- mkCReg(4, 0);

    method Action up(Int#(32) v);
        ctr[0] <= ctr[0] + v;
    endmethod

    method Action down(Int#(32) v);
        ctr[1] <= ctr[1] - v;
    endmethod

    method Action reset();
        ctr[2] <= 0;
    endmethod

    method Int#(32) getCounter();
        return ctr[3];
    endmethod

endmodule

module mkCtrTestbench(Empty);

CRegCounter uut <- mkCounter();

    Stmt teststmt = {
        seq
            action
                uut.up(32);
                uut.down(11);
                $display("Counter is: %d", uut.getCounter());
            endaction
        endseq
    };

    mkAutoFSM(teststmt);
endmodule





Console Dump:
----------------------------------------------------------------------------

bsc -u -sim -g mkCtrTestbench CRegCounter.bsv  checking package dependencies
compiling CRegCounter.bsv
code generation for mkCtrTestbench starts
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__write(...)
  and
    uut_ctr.port1__write(...)
  For the complete expressions use the flag `-show-range-conflict'.
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__write(...)
  and
    uut_ctr.port1__read()
  For the complete expressions use the flag `-show-range-conflict'.
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__write(...)
  and
    uut_ctr.port3__read()
  For the complete expressions use the flag `-show-range-conflict'.
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__read()
  and
    uut_ctr.port1__write(...)
  For the complete expressions use the flag `-show-range-conflict'.
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__read()
  and
    uut_ctr.port1__read()
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port0__read()
  and
    uut_ctr.port3__read()
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port1__write(...)
  and
    uut_ctr.port3__read()
  For the complete expressions use the flag `-show-range-conflict'.
Error: "CRegCounter.bsv", line 40, column 25: (G0004)
  Rule `RL_action_l40c25' uses methods that conflict in parallel:
    uut_ctr.port1__read()
  and
    uut_ctr.port3__read()