When you are using a latched display, as you say, why are you bothering to check "if data has arrived at Port1 " ?

Just keep transferring Port 1 to the display latches at regular intervals - say 1 second ( OK dont use interrupts .Use one of your timers ) or less as is logical to your needs.

( And as to your code , though I have not gone through it line by line , can be made very short with things like loops and look up tables. Find out - its not difficult)

Raghu