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Open drain behaviour for alternative pin functions?

Question asked by lpcware Employee on Jun 15, 2016
Latest reply on Sep 20, 2016 by Mikael Stolt
Content originally posted in LPCWare by pwuertz on Fri Oct 11 09:03:37 MST 2013
Using the PINMODE and PINMODE_OD registers on the LPC1769 I can set an output pin to open-drain mode, which works fine with a pin's default GPIO function. In one of my applications I tried to use the pin P1.22 as an output of the timer match register MAT1.0 in open drain mode. However, the open drain mode seems to be ignored once I switch from GPIO to the MAT1.0 function.

Is this the intended behavior? The user manual (UM10360 Page 105) kind of gave me the impression that the pin mode is independent from the selected function

Quote:
The on-chip pull-up/pull-down resistor can be selected for every port pin regardless of the
function on this pin...

Does open drain only work for the GPIO function?

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