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Rina301

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  1. Hi, Please help with an issue about backdoor read\write to a register. Is it going to be fixed? When doing backdoor write\read to a register – the code (uvm_reg) uses the default map instead of the map the user gave in the write\read register operation: A. do_write gets rw with the correct map that the user wanted – rw.map. B. When doing backdoor write (1 below) , XpredictX (3 below) is called with rw.local_map (=null). get_access with null map is actually default map. C. Even If XpredictX was called with rw.map – it should make many warnings no matter what is the default map\which map we gave the write. This is because in the do_write, Xcheck_accessX (2 below) is changing rw.map to “Backdoor” – empty map which doesn’t contain any regs. ------------------------------------------------------------------------------------------------------------------------- 1. task uvm_reg::do_write (uvm_reg_item rw); -> with the user specified map - rw.map … if (!Xcheck_accessX(rw,map_info,"write()")) (see Xcheck_accessX below ) return; … // EXECUTE WRITE... case (rw.path) // ...VIA USER BACKDOOR UVM_BACKDOOR: begin .. begin foreach (m_fields) begin uvm_reg_data_t field_val; int lsb = m_fields.get_lsb_pos(); int sz = m_fields.get_n_bits(); field_val = m_fields.XpredictX((rw.value[0] >> lsb) & ((1<<sz)-1), (value >> lsb) & ((1<<sz)-1), rw.local_map); -> local map is null – see XpredictX below …. endtask: do_write ------------------------------------------------------------------------------------------------------------------------------------ 2. function bit uvm_reg::Xcheck_accessX (input uvm_reg_item rw, ->with the user specified map output uvm_reg_map_info map_info, input string caller); … if (rw.path == UVM_BACKDOOR) begin if (get_backdoor() == null && !has_hdl_path()) begin `uvm_warning("RegModel", {"No backdoor access available for register '",get_full_name(), "' . Using frontdoor instead."}) rw.path = UVM_FRONTDOOR; end else rw.map = uvm_reg_map::backdoor(); -> rw map is changed to “Backdoor”, local map is not calculated (for FRONTDOOR it is – below) end if (rw.path != UVM_BACKDOOR) begin rw.local_map = get_local_map(rw.map,caller); … return 1; endfunction ------------------------------------------------------------------------------------------------------------- 3. function uvm_reg_data_t uvm_reg_field::XpredictX (uvm_reg_data_t cur_val, uvm_reg_data_t wr_val, uvm_reg_map map); -> map is null uvm_reg_data_t mask = ('b1 << m_size)-1; case (get_access(map)) -> get access is performed with null map = get access is performed without giving a map and it is using the default map instead of the map that the user specified in the write operation "RO": return cur_val; "RW": return wr_val; … -------------------------------------------------------------------------------------------------------------
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