In SX Microcontrollers, SX/B Compiler and SX-Key Tool, SteveW wrote:

The capacitors to ground on IO pins are a dreadful idea. All that means is that the current pulses to drive the IO to a new level will be even higher. Sure, it'll maybe remove a small amount of the noise when the pin is static, but it's still an abominably bad plan. Resistors are better. Both is best.
First, make damn sure that your power supply is  vigorously decoupled. Feed power into the chip (and decouplers) through a surface mount ferrite bead, and make sure that you always put curreent back where you got it from, to reduce loop sizes. PCB routing is critical. A well-done 4-layer board makes life much easier. On a 2-layer board, you're likely to have to resort to hopping signal tracks around with resistors or wire links, since power and ground (and decouplers)  _must_ have priority. 
Then, you're on to application specific issues. How fast do you need your pins to switch? How big a load are you driving with each pin? Given these answers, you can stick a series termination resistor at the SX end of each track, to slow down the edges as much as possible while still doing the job that's needed. 
If you're driving a load through a resistor already, then aleways, always, always stick the resistor at the SX end of the trace if there's a choice (nd there usually is). 
_Then_, you can start sticking tactical capacitors on lines on the non-SX end of teh resistors, to knock off even more high frequencies. 
However, without knowing anything about your design, layout and software, that's pretty much all the general purpose hints I can offer. Post photos & schematics if you like. 

Steve

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