| ??? 08/31/05 14:06 Read: times |
#100356 - Quartz Responding to: ???'s previous message |
Erik Malund said:
the external quartz (10Mhz) starts every time (although with one particular µC, it was taking 10s to start, sometimes... ).
you definitely have a problem here. a) are the traces to the xtal less than 1cm? b) are the traces to the 2 small caps less than 1cm? c) do you have 10-100nF and 4.7-22 uF acriss the LPC with extremely short traces? a)traces to the xtal are definitely shorter than 1cm b)traces to the small caps are also less than 1cm (on the other side of the board, just opposite the xtal, right next to the pins) c)there's a 10nF just accross the LPC, and 100uF(too big?) + 10nF about 2cm away from 1uC, right next to the other uC. There's one 3.3V switching regulator per uC, and it also supplies power to a CPLD (each), decoupled with a 1uF + 2x10nF (each). maybe a better phrase would be "not hold this pin LOW after a power-on sequence" Thanks for that, it makes sense... Laurent |
