Altera Avalon Bus Slave interface

[Altera_Forum]

Hello! 

 Simple question and straightforward:    I'm building a custom IP core and want to connect it to avalon bus. This (slave) component accepts both read and write data (a master can both read it or write to it) BUT never at the same time. You can either read data, or write data.   Should i use 2 data ports (write_data, read_data) as implied in the avalon bus slave interface, or is there any way to use ONE dataport but then it should be INOUT in direction..   What do you think is the most proper way?   i) read_data OUT port  write_data IN port   ii) data_port INOUT   thanks in advance!

[Altera_Forum]

Best practice is to use separate buses for logic that is internal to the FPGA as it only uses routing resources and no extra logic. 

 Any tristate buffers internal to the FPGA don't actually exist as tristate buffers and are synthesized into multiplexers.  Good luck with designing your IP!

[Altera_Forum]

So.. you are suggesting option (i). 

 Separated read and write data ports. I'll try it anyway its easier than to merge both into a single port!   Thanx for your time

[Altera_Forum]

You create a single bus. One avalon interface to your slave component and use both the writedata and readdata ports. 

 Option 1.  Jake

[Altera_Forum]

--- Quote Start ---  You create a single bus. One avalon interface to your slave component and use both the writedata and readdata ports.   Option 1.   Jake  --- Quote End ---     Hi,   Well you can say that if you view writedata as 0.5 bus and readdata as the other 0.5bus = one bus. It is a point of view anyway.   I will go with you all for option (1) and will add this: if you choose inout, nios will ask for an avalon bridge and this adds the issue of byte mode addressing(according to my old nios, unless altera have changed that).   bidirectional bus best suits external connections as it lessens the PCB tracks by half(this is significant, in general board designers love to go even serial single bit when possible e.g. serdes).   kaz

[Altera_Forum]

Hi  

  On SOPC interface you can have inout port but inside your custom component you can control it using output enable pin. Which drives read data as input to component and write as output from comp....if your interface is 32 bit (both read/write) you can use 2 avalon slave busses otherwise 1 bus can work...   Shaik