In a bowl, mix together plum sauce, pineapple juice, ginger, rice vinegar and salt.
Set aside 1/4 cup of the sauce and put it in the fridge.
Pour the remaining sauce in a shallow glass pan. Add the pork chops and turn them to coat well. Cover with saran-wrap and let marinate in the fridge for 1 hour. (You can prepare the pork chops until this step and cover them and put in the fridge until the next day).
Preheat the bbq to medium heat. Ligthly oil the grill and put the pork chops and baste with the marinade. Close the cover and cook for about 10 minutes or until that the pork chops are browned but lightly pink inside. (turn the pork chops and baste with marinade at mid cooking).
While the pork chops are cooking, put the pineapple slices on the grill of bbq and cook for about 2 minutes on each side or until that they have marks. Serve the pork chops with pineapple slices.