pulp-platform
Truncation of `usage_o` port in `fifo_v3` when parameter `DEPTH` is a power of 2
The usage_o port of fifo_v3 has currently a width of $clog(DEPTH).
This causes the pointer to wrap around to all zeros, if the FIFO has a power of 2 DEPTH and is full. This is an issue for the following exapmle:
localparam int unsigned Depth = 32'd16;
localparam logic [3:0] Threshold = 4'hF;
logic [3:0] usage;
if (usage > threshold) begin
/* do something */
end
This if statement would not trigger in this case.
This could be resolved by assigning the whole status_cnt_q to the usage_o port instead of the truncated one as is currently the case.
The workaround I am using currently is prepending the full_o signal to the ussage_o, however this causes jumps in this new usage pointer value when the FIFO is not configured to a power of 2 DEPTH.
Good catch and thanks for reporting. We should probably fix this in a fifo_v4 or a breaking change (major version bump) in the common cells repo (which is unfortunately anyway required near term).
