Currently I am designing my own device with W5100 chip and Atmega644 micronontroller.
I would like to utilize SPI bus for communication between both chips. I’ve already read datasheet, I’ve seen reference schematic as well, but few issues are still unclear for me.
- What should I do with /CS, /WR and /RD pins, when I am using SPI instead of parallel bus? Should I left them unconnected, or rather pull them up to VCC with single resistor, just like in case of Arduino Ethernet board?
- What should i do with SEN pin? Should I simply pull it up to VCC? I am asking, because there is some strange solution with inverting buffer on the Arduino Ethernet board schematic.
- Should I left DATA pins unconnected, or connect them to GND, just like on the schematic of Arduino Ethernet?
- Can I connect GNDA pins to the common ground plate, without using ferrite bead?
- Is it possible to use single SPI bus for W5100 communication ans ISP Atmega programming? I mean, does chip sets high-Z state on MISO, when SPI is not used (SCS line in not active state)?