Hi,
I am getting the following warning: WARNING:Xst:1778 - Inout is assigned but never used. My AddrBus is bi-directional and I am following example suggested here:
I am writing to the bus outside of process. Why would I get this message? It looks like the signal is used. here is the code:
architecture Behavioral of controller is begin ... ... AddrBus 'Z'); ... ... end Behavioral;
Is this portion in your top level entity? Or is a sub entity?
-Isaac
For now, this is my top entity, but there'll be something else higher in the hierarchy later on. Another entity will be using AddrBus for reading from it as well. For now, there's only writing implemented as I am accessing memory at specific location.
Isaac Bosompem wrote:
I think it is doing this because you are not using it as an input. Also if you are working with FPGA's I think it would be a good idea to only use unidirectional ports in sub modules. While using bidirectional ports for top level devices (SDRAM, SRAM, Flash, etc.)
-Isaac
I think it depends on actual FPGA. On those ones that support 3-state buffers in their units (e.g. Virtex) it's fine, if you really need it of course. On the other hand on something like Spartan, where 3-states are not supported (except IOs), implementation of
3states is based on logic chain which is, probably, not the best way :)My device is Spartan 3. The RAM blocks were used by one of the modules which beside RAM included some memory bank decoders. RAM blocks were instantiated by that module. I wanted to have bi-directional bus going from this module to another one. For now, I had to disable that and use separate busses as a quick fix, but I think in this situation bi-directional busses should be supported. What do you think? Note that the bus might not actually be visible from outside of fpga, so there are no ports involved.
Alexey L> >
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