SystemRDL defines the swacc property, but it does not distinguish between read and write operations - it is asserted on all software accesses. Similarly, the spec defines swmod which gets asserted on software writes, but can also get asserted if the field has on-read side-effects.
What if you just wanted a plain and simple strobe that is asserted when software reads or writes a field? The rd_swacc and wr_swacc UDPs provide this functionality.
These UDP definitions, along with others supported by PeakRDL-regblock can be enabled by compiling the following file along with your design: regblock_udps.rdl <../../hdl-src/regblock_udps.rdl>.
rd_swacc
If true, infers an output signal hwif_out..rd_swacc that is asserted when accessed by a software read operation. The output signal is asserted on the same clock cycle that the field is being sampled during the software read operation.
- {"signal": [
{"name": "clk", "wave": "p...."}, {"name": "hwif_in..next", "wave": "x.=x.", "data": ["D"]}, {"name": "hwif_out..rd_swacc", "wave": "0.10."}
]}
wr_swacc
If true, infers an output signal hwif_out..wr_swacc that is asserted as the field is being modified by a software write operation.
- {"signal": [
{"name": "clk", "wave": "p....."}, {"name": "hwif_out..value", "wave": "=..=..", "data": ["old", "new"]}, {"name": "hwif_out..wr_swacc", "wave": "0.10.."}
]}