Hi,
Only four pins on PortB have the interrupt on change capability and the interrupt is tripped when either one of those four changes state (if enabled). On the 16F677 you can enable/disable the interrupt on change feature for the four pins individually so if you only want one pin to trip the interrupt you simply enable the interrupt for that pin only. See section 4.4.2 in the datasheet for more info on how you do that.

Older PICs like the 16F877 doesn't allow you to enable the interrupt for indvidual pins like you obviously can on the 16F677 - nice feature.

HTH
/Henrik.