Im looking at connecting an Ethernet shield upto one of our own 8051 based microcontrollers at work. Put together a really simple webserver based app on the Arduino, and stripped it back to a series of SPI writes in prep for the port. Run in on the 8051.....no response. Trace the signal lines with a Saleae Logic. Correct data out of our chip on MOSI but nothing on MISO. Plug the Ethernet Shield back into the Arduino....everything is fine.
OK. Must be a hardware problem. Connected up the 4 SPI pins (CS, MOSI, MISO and CLK) from the Arduino to the Shield via jumper cables. Added the power supply pins as well. Run the Arduino and get same behavior. Nothing on MISO again. However its fine when running directly plugged in.
Ive looked in the W5100 datasheet and cant see anything that needs to be pulled low/high apart from the SPI_EN pin which is taken care of by the shield.
Anyone got any ideas on whats happening?