power on reset pin status

[rahulkrishna]

Hi I am facing a very difficult problem, I have given one of the port J port to control an output pin. So when required i will give either 1 or 0 based on requirement. The problem i am facing is on power on reset this pin is a high and my output is going high. when the control comes to maintain i am able to initialize. Please advice me how to control this pin so that on power on or reset i can make it a low. I am using S12x.

[RadekS · Accepted solution]

Hi rahul,

I suppose for now that you use MCU from S12XD Family.

The default status of port J pins is digital input with enabled internal pull-up after reset.

Please look at Table 1-7. Signal Properties Summary in RM.

I could see two basic possible solutions:

1.    You could select different pin for driving that external circuit. In that case, you could choose pins with default pull-down (no such pins for S12XD family) or pins with default disabled pull-device (port A, B, C, D, H, M, P, T, AD). When we select pin with default disabled pull-device after reset, we should use external pull-down for ensure that voltage level will stay low until we configure this pins as outputs.

2.    Internal pull-device is weak. We could assume that internal pull-up value is higher than 25kOhm. In that case, we could use external strong pull down (for example 2.2kOhm) at port J for ensure that that voltage level will stay low (below 0.8V) until we configure this pins as output.

I hope it helps you.

Have a great day,
RadekS

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[rahulkrishna]

Thank you very much for the reply. It feels great that now a days we get reply in very short duration. Sorry that i did not mention my micro it is S12xE family.