Using an external digital clock on ECO input pins

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Using an external digital clock on ECO input pins

Postby Dagodevas » Thu Jan 23, 2014 12:58 pm

Here's an excerpt from AN54439 concerning external crystal oscillators:
Using an External Clock Signal on the ECO Pins
If the MHz or kHz ECO is not being used, an external clock signal may be routed onto the ECO clock nets using the kHz or MHz crystal input pins. This allows the use of these clock nets in place of the usual DSI clock net in the clock tree. External clocks can be routed into the part through the kHz and MHz XtalIn pins. The XtalOut pins should be allowed to float. Ideally, the external signals should be rail-to-rail sine or square waves. If the amplitude of the signals is too low, they may not be properly translated into digital signals. These signals must be within the frequency ratings of the ECOs, either at 32.768 kHz or 4-25 MHz.
External clocks can also be routed into the part using the GPIOs. For more details, see AN60631 - PSoC® 3 and PSoC 5LP Clocking Resources.


I want to use MEMS oscillators for both the MHz ECO and the 32khz ECO. It sounds like I can tie them right to the input of each ECO, but it doesn't say anything about how I would need to set it up in Creator. It has all the parameters for fine tuning the crystal such as fault recovery, amplitude adjustment, and reference levels. Anyone know what settings I would use in this case? Also, it says it should be a rail to rail input, but which rail are we talking about? I'm planning on using 5V for all but one or two ports, but the MEMS oscillators seem to be 3.3V max most of the time. It seems like the VDDIO for the port where the ECO pins are located would not have any effect since the pin is being used in a different mode, right? Some guidance would be greatly appreciated.
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Re: Using an external digital clock on ECO input pins

Postby danadak » Fri Jan 24, 2014 2:49 pm

I think this is being handled on cypress forum, and I have sent a
message to max for comment on the cypress thread you started.

You could also post a case -

To file a tech case -

www.cypress.com
“Support”
“Technical Support”
“Create a MyCase”

Regards, Dana
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