SCL Reference: Shared Location
SCL allows the reading and writing of general purpose memory locations. But, you have to declare a shared location in the configuration section.
shared location varName := locationAddress;
configuration for "PIC16F877" is shared location loc70 := #16#70#; end configuration; testbench for "PIC16F877" is begin process is begin wait on loc70; if loc70 == 0 then loc70 <= 1; else loc70 <= 0; end if; end process; end testbench;