'''Notes'''
* On type 0 The CRTC is not connected to the CPU's RD and 1WR pins, so the CRTC is not aware of the CPU bus I/O direction. Therefore, if a Write Only register is read frominstruction is used on a write register of the CRTC, "0" then a data is returnedsent to the CRTC.
* CRTC On type 4 0 and 1, if a Write Only register is the same as read from, "0" is returned. * CRTC type 3. The registers also repeat as they do on the type types 3and 4 are identical in every way.
* See the document "Extra CPC Plus Hardware Information" for more details.