I'm currently designing a media converter board using Vitesse VSC8221. Just as an FYI, the documents for this product are all available at the product page. No NDA is required.
When I say media converter, I actually meant SFP interface for fiber medium to RJ45-CAT5 for copper medium, and vice versa.
Now, I've studied the datasheet and application notes of the chip quite extensively, and the chip does offer a 'Media Converter' mode (Datasheet:Section 4.2:Page 2). The application diagram for this mode is as shown below.
While I can use this mode, one drawback of this mode is that it only supports 1000BASE-T to 1000BASE-X. It doesn't support conversion to/from 10/100BASE-TX.
But in the datasheet, it's also showing a mode where it supports all 10/100/1000BASE-T to GBIC/SFP interface. The application diagram is as shown below.
Now, my questions are: Can I use the second mode to do my media conversion? I know there are copper SFP also, but since the interface is specified as SFP, what's stopping me from using an optical transceiver SFP? If the Fiber-SFP(eg to MAC) can transfer data both ways, why can't I simply put my optical module at the SFP signal pins and get it to work as optical-copper converter instead?
If no, does this chip allow me to do a one-chip media conversion that supports all 10/100/1000BASE-T, even if that means I can't use the 'Media Converter' mode? I've read the datasheet and I'm still not sure of the answer.
I hope someone can offer some advice on the matter. Thank you so much in advance.