In the datasheet XI/XO are described as analog pins. If a crystal is used the ground should be connected to AGND. While if an external clock is used it should be sourced with analog 3.3V and AGND.
But I’m not sure about this, because XI/XO seem also involved with digital part of the chip. Reasons are as below:
- The MAC part needs clock too. So they must be sharing the same source?
- I checked ref schematic of W5300, which seperates analog and digital grounds strictly, to find that all kinds of clocks use the digital ground. So I guess w5500 could be similar? However in all ref schematics of W5500 there is actually only one ground…
- Not very seriously, but I find that pins of W5500 are seperated into analog and digital sections and this is reasonable. The XI/XO are just located in the digital section, if there is such partition.
Currently I’m going to have a common ground and use an external clock. Should I power the clock source with analog or digital power? Thanks!