GPIO SPECIFICATION on msp430f2252 for rise time and fall time

There is no single rise tiem or fall time.
The actual timing depends on:

- supply voltage
- resistive load
- line capacitance

You can determine th evalues for your particular situation from the device datasheet: maximum GPIO frequency for two specific supply voltages and actually the diagrams for output voltae over load. You can create a dynamic calculation where the line resistive load and hte lien capacitance forms a changing Z and therefore a changing output voltage and determine over the capacitacne loading time the required delay before the output voltage reaches your desired trigger voltage.
Since there are so many variables in this process, there is no sense in providing dedicated values.

The fact that there is no 'the rise time' over all operationg conditions is because of the low power design. A constant rise time over all operating onditions would greatly increase the oputput driver power consumption (for all condiitons!), which is not desireable for a device that is supposed to work down to the the sub-µA range.