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It depends on your design.
If the bus is shared within a small block, perhaps mux isn't a bad idea. But if the bus is shared by some blocks which may be placed seperately in layout, tri-state style is more suitable for area/routing consideration. And some small bus keeper may be needed.
For this application it is definetely better to use tri-state bus! But do not forget to implement the kind of bus arbiter if you will have more than one master on the bus!
Timing and testing in tri-state bus implementation is a problem.
The designers don't take more time to trim timing problem by using mux-based bus.
In SOC design, all most designs choose mux-based bus, because IP integration is easier.
Another benefit of the mux-based bus is to improve bus bandwidth efficiency significantly, eg. AMBA 2.0.
I think it is not possible to say this is better then.... Normally you have a look on the chip you are using, e.g. Altera ´have no internal tristate busses, they can only build external tristate Busses. This feature will only be in Xilinx FPGA's.
What is your design. If you design a uC board or ... . Tri state bus is better.
But if you design an SOC or ASIC (or both) it deoends to your vendors as menthioned above.
From my point of view, mux is make the design easy to implement. However, tri-state bus style is good for large design with many block. And it need more effect on layout backannotion.
It depends on your design.
If the bus is shared within a small block, perhaps mux isn't a bad idea. But if the bus is shared by some blocks which may be placed seperately in layout, tri-state style is more suitable for area/routing consideration. And some small bus keeper may be needed.
Our ASIC design practice is: inside the chip, MUX only. No tri-state.
External bus, tri-state if necessary.
Tri-state has problems such as timing and power consumption, as posted by another fellow. Avoid tri-state if you're doing ASIC design.
FPGA is different. FPGA devices have tri-state buffers built in. In some cases, it makes sense to use those tri-state buffers to drive long lines that are shared by blocks. This trick reduces routing congestions. However, tri-state buffers are slow, be aware of it.
In my experience the "which is better" debate would be "it depends if your
tools can support the methodology". If your tools can cope with the
contention and undriven aspects of tristate buses, then bidirects are usually smaller and cheaper to use. But if your tools expect logical connections only, then it is best not to use bidirects because sooner or later you will come across a situation when the tools misses a logical driver error resulting in contention, or worse a float.
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