Re: [partial-reconfig] Bi directional bus macro?

[Ian Colwill <I.Colwill@xxxxxxxxxxxx>]

Maybe I should elaborate! Please excuse the newbie question; I have 
little experience in FPGA design.

I want to connect three (or more) reconfigurable modules via a bus 
macro. The Xilinx bus macros can only directly connect two modules. The 
arrangement I am looking for is a shared bus situation as in figure 
below between three or more modules.

(This diagram is for one bit of the four bit bus)

I am trying to produce a macro using FPGA editor and / or xdl (via xdl 
-xdl2ngc). The problem I’m having is I cannot route the output of more 
than two TBUFs to the same TBUF Line.


Using xdl I have managed to make a logical connection between three TBUF 
outputs (two existing TBUFs and my “new_tbuf”) using the following code…

net "TNET<3>" ,

cfg "_NET_PROP::IS_BUS_MACRO:" ,

outpin "t1E_<3>" O ,

outpin "t1A_<3>" O ,

outpin "new_tbuf<3>" O ,

pip R1C9 TBUF_OUT0 -> TBUF2 ,

pip R1C10 TBUF_STUB3 =- TBUF3 ,

pip R1C13 TBUF_OUT0 -> TBUF2 ,

# net "TNET<3>" loads=0 drivers=3 pips=3 rtpips=0

;

But the design fails to route in fpga editor giving the error message…

ERROR:FPGAEditor:553 - Selection contains no signal pin. Manual routing

requires the selection to include at least one pin of the signal, or a wire

that is already a part of the partially routed signal.

ERROR:FPGAEditor:361 - Nothing found to route.



Does anyone know why this is? I’m sure there is an obvious reason I’m 
just not seeing it.

Does anyone have another solution to connecting multiple reconfigurable 
modules that does not involve having two busses (one going left and one 
going right) or having a message passing scenario between adjacent modules?

Thanks in advance for any advice or ideas you may have.

Ian.









Ian Colwill wrote:

> Hi, has anyone built a bi-directional bus macro? I have tried to build 
> one with little success. My attempts fail during the final PAR stage!
>
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