Hallo Jason,

connect from each Port0 pin a resistor of about 10kOhm to +5V. Then, check again voltages at output of Port0 pins. Now they should show logic high state after invoked reset.

These pull-up resistors are used at Port0 lines, if you use them as nominal port outputs. If you use them for accessing external memory, on the other hand, then these port lines behave different. Then, you don't need any pull-up resistors!

Internally, either only an NMOS output transistor is present, so that output looks like open drain, needing a pull-up resistor, or a push pull stage consisting of PMOS and NMOS transistors is present not needing any pull-up resistors.

Which sort of output is present is controlled by you! Whenever you address external memory, means, whenever you use MOVX instruction, for instance, push pull output stage is present, but only for the duration of according MOVX instruction.

Kai