hwset on multibit field about peakrdl-regblock HOT 5 OPEN

In SystemVerilog, the '1 literal (with a leading ') is a shortcut to assign all bits of the assignee to ones.
For example:

logic [31:0] example;

// The following two lines are equivalent
assign example = '1;
assign example = 32'hFFFFFFFF;

// Not to be confused with:
assign example = 1;
// which is identical to:
assign example = 32'h00000001;

from peakrdl-regblock.

Sorry, yes, that's correct; however, my expectation was that the hwset port would be 32 bits wide, and each bit would be set independently, not all at once.

That being said, the spec says "set the field (hwclr and hwset) by asserting a single pin" and so perhaps my expectation is wrong. Allowing each bit to be set independently seems more useful than setting all bits, but perhaps my use case is unusual.

Is there a better way to accomplish this? Do I need to manually add 32 1-bit fields with the hwset property?

from peakrdl-regblock.

Ah I see. I misunderstood your question.

That is correct - for the hwset property, it infers a single-bit input to set all bits.

Aside from splitting to individual 1-bit fields, if you want to set individual bits in a field you probably have to handle this outside of the regblock. I can't think of a good way to do it entirely in RDL. One way would be using the hardware write-enable mechanism:

field {
    sw = rw;
    hw = rw;
    we;
} b[31:0] = 0;

Then in RTL use the write-enable to apply the updated per-bit set behavior:

assign hwif_in.a.b.we = |my_bit_set_vector;
assign hwif_in.a.b.next = my_bit_set_vector | hwif_out.a.b.value;

from peakrdl-regblock.

Thank you! And thanks for PeakRDL!

Would you be open to a PR which added an option for this? I'm not sure if I'm going to take that on right now, still evaluating, but thinking about it. It's useful enough to us.

from peakrdl-regblock.

Sure! I can see how this could be useful.

This would definitely have to be a separate property. Changing the behavior of hwset and hwclr would be inappropriate since the SystemRDL spec pretty clearly dictates this is a single-bit strobe to set/clear the entire field (I actually use hwclr like this on multi-bit fields intentionally in some applications)

I would recommend implementing this as separate user-defined properties like bitwise_hwset and bitwise_hwclr, much like some of the other extended properties I have implemented.

from peakrdl-regblock.