I'm making a board with MCP2515T-I/ML due to space constraints and it won't start up.
The top layer copper pour is 3.3V and the second layer is a solid ground plane.
I have checked for shorts, there are no shorts. I have checked the MISO, MOSI, CLK and CS lines and they all behave appropriately excluding MISO. It seems not only does the MCP2515 not want to turn on but the 8MHz external clock is not oscillating. I checked using a tiny SA and a H field probe (which correctly detects oscillations of other crystals).
I have conducted both manual hardware reset and SPI reset on the device and attempted to communicate with it, it still doesn't communicate.
After replacing the MCP2515T-I/ML multiple times on different boards I'm beginning to wonder if the issue isn't only that the crystal never starts up and the MCP2515 remains in "oscillator startup timer reset mode".
The crystal is ABM3B-8.000MHZ-10-D-1-G-T.
The crystal load capacitor is 10p and I've replaced the crystal as well, no dice. I don't currently have 0402 capacitors to vary the load capacitance but am wondering if the 3.3V top layer copper pour could be providing so much parasitic capacitance that the board needs to be redesigned. According to C1,2 = 2(CL-Cstray), I should have used C1,2 = 14p if Cstray was 3p. Supposing Cstray is much higher I may not have needed to use any load capacitors. In desperation I've removed the load capacitors one at a time and attempted to see if the crystal would oscillate, in case the parasitics were in excess. That didn't work either.
I don't feel comfortable sending off a redesign until I know exactly what went wrong here, since it could be multiple things. I'm aware I should have had a keep out area and guard ring in the top layer around the crystal. Would that be the only issue though?
If possible I'd like to measure the actual load capacitance but my MM doesn't seem up to the job. The capacitance value measured across one load capacitor is either hovering around 12p or 2n.