Why External Phy?!

[rdazcal]

Please excuse my ignorance:

Why is it that most freescale's MCUs use external PHY instead of internal PHY like the MCF5223x family?

Is it to offer the possibility to connect to means of communications other than Ethernet?

I thank you in advance.

[gmnelson]

Good question!  I have a couple reasons "why an external PHY?"

An external PHY gives our company the opportunity to provide a Fiber ethernet connection as well as the standard copper ethernet option.

Also, an external PHY gives us the ability to 'ruggedize' the ethernet input hardware.  That is we can add circuitry (transorbs etc.) that protects against harsh environments where voltage spikes and transients happen regularly.

[rdazcal]

Thank you gmnelson

[scifi]

I was thinking the same thing.

If MCF5225x had a built-in Ethernet PHY, it would be almost perfect for my current application.

But I have to say that the PHY in MCF5223x has its drawbacks. It's too power-hungry, auto-negotiation is broken, missing automatic MDI/MDI-X detection.

There must be some cost associated with a built-in Ethernet PHY. Substantial silicon area, could interfere with the ADC, maintaining or licencing a PHY has a cost too. I'm just speculating here, though...