we are operating a MC9S12XDP512 / MC9S12XEP100 micro controller in expanded mode. On the external bus a static RAM IC is connected without external pull up / down resistors on data bus.
What is your the recommendation regarding pull up / down resistors:
- do we need pull up or pull down at all on the external data bus to have a defined signal level in case the external static RAM IC is not accessed?
- should / can we make use of the internal pull up feature of PORT C / D to have defined signal levels on the external data bus (set PUPDE PUPCE in PUCR register)?
- should we better use external pull up / down resistor to have defined signal levels on the external data bus?
- is there an application note about this topic and where do we find it?
We are looking forward to get an answer to the questions soon.
With kind regards