Hi All,

I've been thinking about this in a 'back-burner' sort of way. My understanding is that push-pull ports can be used for inputs or outputs--I use a Cygnal chip with pins of each configuration, and I like the fact that Cygnal allows full configuration on all pins. However, on traditional 8051s, only P0 was open-drain--unless I misunderstood the last post on this, that would mean only one port could be used as inputs. I believe that to use a push-pull pin as an input, you have to write a '1' to it first, and then the external device will either pull it low, or not so that you can read the external device. I double checked my Intel MCS51 Microcontroller Family User's Manual, and it mentions that writing a '1' to the pin disables the output FET. Please let me know if I'm off track on this...

Best To All,

Josh