UVM RAL adapter for APB transaction

UVM
1

Hello guys,

I am developing a uvm_reg_adapter with apb transaction

in the reg2bus function, const ref uvm_reg_bus_op rw.
my doubt is for apb bus we have separate bus for write as well as read data. so how to handle this??
I have written code like below. can someone help me on this

virtual function uvm_sequence_item reg2bus(const ref uvm_reg_bus_op rw);
apb_pkt= apb_packet::type_id::create(“apb_pkt”);

  `uvm_info("apb_ral_adapter","Executing Reg2Bus",UVM_HIGH);
  `uvm_info("apb_ral_adapter",$psprintf("Got register transaction :addr=  %h  bit: %h  data=%h  kind:%h ",rw.addr,rw.n_bits,rw.data,rw.kind),UVM_FULL);

// 32 bit data transfer
if (rw.n_bits > 32)
`uvm_fatal(“apb_ral_adapter”, “Transfer requested with a data width greater than 32bit data width. Please reduce the data size”);

 `uvm_info("reg2ahb_adapter", $sformatf("n_bits data = %b log_base_2 n_bits", rw.n_bits), UVM_HIGH);
  apb_pkt.apb_trans = (rw.kind == UVM_READ) ? apb_packet::APB_READ : apb_packet::APB_WRITE;
  apb_pkt.apb_paddr = rw.addr;
  if(rw.kind == UVM_READ)
     apb_pkt.apb_prdata = rw.data;
  else
     apb_pkt.apb_pwdata = rw.data;
  return apb_pkt;

endfunction : reg2bus

// apb_packet has the following fields
rand enum {APB_READ,APB_WRITE} apb_trans;
rand bit [31:0] apb_paddr;
rand bit [31:0] apb_pwdata;
rand bit [31:0] apb_prdata;

2

I guess your confusion comes from the fact that your APB items contains both a pwdata and a prdata field. Ideally it should have only contained a single pdata field that would contain the value to be written to pwdata for a write transaction or the value read from prdata for a read transaction.

When calling reg2bus(…) you are constructing the transaction that will be executed on the bus. The key here is that the transaction wasn’t executed yet, so for a read, you have no idea what it will return. After the transaction is finished, the driver should update the prdata field with the value actually read from the DUT. The register layer will then call bus2reg(…) on this item which will update the data field of the register item.

Long story short, for reads, reg2bus(…) does nothing, for writes bus2reg(…) does nothing.

3

In reply to Tudor Timi:

Thanks a lot Tudor. That was helpfull