15-cell addressable memory

[immibis]

rarebed
The inputs are on the left.
When a crate or barrel enters the top input, data will be read from the specified address (0 is not a valid address).
If there is a crate or barrel waiting in the bottom input, it will be written to that address, and the previous contents of the cell will be read and output.
Otherwise, the current contents of the cell are read and output.
More than one read operation may be waiting behind a write operation, but if multiple write operations are waiting to be processed the behaviour is undefined.