VHDL-Code with Avalon Bus Interface-/ and VHDL-Video-System-Interface-Ports

you don't want to use the avs_dataavailable signal. Either create an interrupt that is triggered on the new state, or create a register you can read/poll that has the status of the new coordinate state that can be cleared when you read it. i have never used the dataavailable signal, but if you were to use the avalone bus to indicate when data was ready to read you would have to issue a read and the bus would hang until the new coordinate was present, which is most likely not what you want.