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KL17 FlexIO - Shift Neg Clock Edge - No Shift takes place

Question asked by joe hinkle on Nov 7, 2016
Latest reply on Nov 17, 2016 by joe hinkle

The FlexIO is pretty straight forward -- that's why this is perplexing me.

 

FlexIO described her and in KL reference manual:  https://community.nxp.com/docs/DOC-105640

 

Here is the data and clock output from a FlexIO data and clock channel. -- I'm only showing the first data bit because I'm interested on what edge the data shift out.

 

 

Here is a similar image from the reference post above.

 

 

In both cases, the data is shifting out on the rising (positive) clock edge.

 

I want my data to shift on the falling (negative) clock edge.

 

As noted in the 2nd image above, all one SHOULD have to do is to change the Shifter Control TIMPOL value from 0 (shift positive edge) to 1 (shift negative edge) ... as shown in second pic above.

 

When I set TIMPOL to shift on falling edge -- the complete shift operation STOPS!!  NO data comes out the shifter pin.

 

I return TIMPOL back to 0 and all shifting operations work -- "on rising clock edge"

 

Can someone please comment on what the issue may be?

 

Thanks.

 

Joe

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