1. The function of this I/O port is dependant on the CRTC type
2. The CRTC is not connected to the CPU's RD and WR pins, so it cannot detect the CRTC is not aware of the CPU bus 's I/O direction. Therefore, if you perform executing an IN instruction to the select or write functions, it will write data to causes the CRTC from to write the current unpredictable data on provided by the high-impedance busto its registers.
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