I2C loopback on Max II

[Altera_Forum]

Hi, 

 I'm trying to figure out a way to do a I2C loopback test. How do I handle the bidirectional data, without actually implementing the logic of reading the R/W* bit on the address sent out? I know which is the master & which is the slave ahead of time.  In essence, I guess, is there way to synthesize a bidirectional buffer?  appreciate your help.

[Altera_Forum]

I don't exactly undertand what an i2c loopback test is. But I doubt, that you can operate an I2C interface without evaluating the direction information, respectively the adressing and read/write state. 

 A digital bidirectional buffer, e.g. a HC245 device, can't work without DIR control. Special I2C buffers are either utilizing analog bus swiches or an analog direction sense detector, both aren't available with CPLD or FPGA.

[Altera_Forum]

basically, testing two I2C ports on a device.. connecting them together in a CPLD & configuring one as master & other as slave on the device. Of course, I am testing other features as well using the CPLD. This is just a part of it. 

 Thanks

[Altera_Forum]

Use an external bus switch.

[Altera_Forum]

The whole point of the CPLD is to reduce external components.. so I'm guessing from your replies, I will need a GPIO into the CPLD to tell me when data direction switches..

[Altera_Forum]

--- Quote Start ---  I will need a GPIO into the CPLD to tell me when data direction switches  --- Quote End ---   Yes, if you where you get it.