Instruct the compiler to generate code for 8-bit LCD displays attached to the data bus.
$LCDRS = [&H]address
The address where must be written to, to enable the LCD display and the RS of the LCD.
The db0-db7 lines of the LCD must be connected to the data lines D0-D7.
The RS line of the LCD must be connected to the address line A0 by default.
When it is connected to another address line you can specify $LCDRS
On systems with external RAM/ROM it makes more sense to attach the LCD to the data bus. With an address decoder you can select the LCD display.
$lcd = &H8000 'writing to this address will make the E line of the LCD high.
$lcdrs = &H8002 'writing to this address will make the RS line of the LCD high.