I was doing some research on Embedded Ethernet and found some
interesting results that may be useful to others:

1) Micro-controllers with embedded 10/100 Ethernet controllers implement
only the MAC, you will need an external PHY.
2) 10/100 MAC only available in 32-bit devices.
3) To interface to a PHY it is necessary either 10 (RMII) or 18 (MII)
pins, all but three exclusive to the PHY. The other three can be shared
with other PHYs if you have more MACs in the MCU.
4) Micro-controllers with otherwise identical characteristics are around
$0.27 cheaper without Ethernet.
5) PHY chips cost around $3.98 @ 1 or $3.54 @ 100.
6) a - ENC424J600 is a complete 10/100 Ethernet controller (MAC+PHY).
    b - Costs around $4.56 @ 1, $3.58 @ 10, $3.29 @ 25 and $2.98 @ 100.
    c - Can be interfaced with the MCU either with 4 pins (SPI) or 12 or
more pins (parallel), most of which can be shared with other devices.
7) Most MCUs with embedded Ethernet have only one MAC, some rare (very
big) ARM MPUs have two (need external SDRAM and FLASH, you loose code
protection).


Conclusion:
ENC424J600 (or ENC624J600 perhaps) will cost less and waste less pins of
the MCU than using a MCU with embedded Ethernet controller, and you will
have a much wider range of MCUs to choose from.
The only point in favor of an external PHY is if you need to use almost
all of the 100Mbps bandwidth, then the ENC424J600 cannot keep up to the
data flow (maximum 14Mbps with SPI and 80Mbps with parallel interface).


I was considering using a PIC32MX device with embedded MAC plus an
external PHY for a new project, but now I'm biased towards a PIC32MX
without MAC plus an ENC424J600 (PMP port shared between ENC, NAND-FLASH,
keyboard and LCD module).


Best regards,

Isaac

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