Changes
/* Controlling the Gate Array */
The recommended I/O port address is &7Fxx.
The Gate Array is not connected to the CPU's RD and WR pins, so it cannot detect the bus's I/O direction. If you execute an I/O read operation on the Gate Array I/O address, the Gate Array will read an unpredictable value from the databus which will be in high-impedance state. If the value is a valid Gate Array command, it will be executed, otherwise nothing will happen. [https://www.grimware.org/doku.php/documentations/devices/gatearraydo=export_xhtml Source]
The function to be performed is selected by writing data to the Gate Array, the first bits of the data define the function selected (see table below). It is not possible to read from the Gate Array.
