Am Mo 10. März 2008 schrieb Andy Green: > - gpg control packet > Somebody in the thread at some point said: [...] > > Also, you said the PCLK signal is very corrupted due to the R-C. Even while > > apparently not causing actual trouble, this should be given a closer look, to > > feel good regarding worst case scenarios. Someone has to have an explanation > > _why_ this C is there and should be this value. Otherwise just replace with a > > better value for MP? > > I guess the idea is emissions LPF... I attach what it does to this > 24.5Mhz clock. This is on a 200MHz bandwidth 'scope, that's really what > the "square wave" actually looks like at the LCM connector :-) > > If there is no objection maybe we could try 12pF or somesuch there > instead of 47pF. But at this time near production I can imagine the > urge is to let all sleeping dogs lie. > > -Andy >
From LCM-datasheet: abs. max. ratings: (for PCLK, @VDDIO=3,0V) VInput-Low: <= VDDIO * 0,3 = 0,9V VInput-High:>= VDDIO * 0,7 = 2,1V I think this scope-plot signals really critical situation for PCLK. NB: with higher clock freq , situation gets worse! cheers jOERG
