Solution:

The C&T65545 VGA controller provides two registers for changing text and graphics video output polarity. To do this, user must use Index register to select XR61 or XR63 register and then change bit 7 of both registers in application program. Extension Index Register( I/O=3D6h) The register is used to select what register you want to read/write. XR61: SmartMap Control Register (I/O=3D7h, index=61h) The bit 7 of XR61 is effective for flat panel text mode only. 0: Normal Polarity 1: Inverted Polarity XR63: SmartMap Color Mapping Control Reister (I/O=3D7, index=63h) The bit 7 of XR63 is effective for CRT and flat panel graphics mode only. 0: Normal Polarity 1: Inverted Polarity