'''Notes'''
* The CRTC is not connected to the CPU's RD and WR pins, so the CRTC is not aware of the CPU bus I/O direction. Therefore, if a read instruction is used on a write register of the CRTC, then a data is sent to the CRTC.
* On types 0 and 1, if a Write Only register is read from, "0" is returned.