UNO Ethernet Reserved Pins

Using Arduino Storage
1

I wasn't sure where to post this, so I hope this works.

I've got an UNO Ethernet, and I know that pins 10-13 are reserved and can't be used for I/O, but what about pin 4?

Pin 4 is reserved for the SD card... but what if I don't want to use the SD card? Can I use pin 4 for I/O?

I can't seem to find anything telling me that I can't use pin 4.

Anyone know?

2

You can use pin 4 for I/O if there is no SD in the socket. Pin 4 is only connected to the high-Z input of a level shifter IC.