Need to know about using the PTA2/KBIP2/CLK/nRst/VPP for input

[llester]

We have literally tens of thousands of the MC9RS08KA2 in stock so Im trying to continue using it for a product upgrade. The problem that im facing is that i need one more input.

My hope was to put two push buttons with in parallel on this pin. pusing one would give 0 volts and the second would give 2.5v and the pin would normall rest at 5 volts if no button was pressed.

I know that the reset can only be used as a Input but is is possible for it to detect different voltage levels?

PTA2/KBIP2/CLK/nRst/VPP

The IC will be pre programmed so I will not need the reset and or VPP.

[peg]

Hello,

Don't know how many buttons you already have but I have put three buttons on two inputs before.

It was up/down enter. Up and down where connected as normal and enter had a diode to both up and down.

When you got an input, straight after the debounce check for the other input, if it's on its enter or up/down if it's not.

[bigmac]

Hello, and welcome to the forum.

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llester wrote:

I know that the reset can only be used as a Input but is is possible for it to detect different voltage levels?

PTA2/KBIP2/CLK/nRst/VPP 

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The short answer is no!  This input is only capable of detecting logic high or logic low levels.

Your only hope would be to reallocate the comparator input for the pair of switches (with the other input of the comparator connected to the bandgap), but this would only be likely to work for Vdd 5.0 volts.  The method will not work for Vdd 3.3 volts, and lower.

This concept is to utilize the difference between logic low switching threshold (1.5 volts minimum @ 5V Vdd) and the bandgap reference voltage (1.16-1.23 volts).  One of the switches must present an input level within the limits 1.23-1.5 volts, and the other switch an input level of less than 1.16 volts.

You would firstly sense that a logic low condition was present, and then enable the comparator input to determine which switch was the active one.

Regards,

Mac