FEC FEB-9455, Руководство пользователя

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FEB-9455 User’s Manual 53
Value of Inversion Register:
Only lower nibble is available for this function.
When set to a ‘1’, the incoming/outgoing port value is inverted.
When set to a ‘0’, the incoming/outgoing port value is the same as in Data Register.
Value of I/O Selection Register:
Only lower nibble is available for this function.
When set to a ‘1’, respective GPIO port is programmed as an input port.
When set to a ‘0’, respective GPIO port is programmed as an output port.
Value of Output Data / Input Data:
Only lower nibble is available for this function.
If a port is assigned to be an output port, then its respective bit can be read/write.
If a port is assigned to be an input port, then its respective bit can be read only.
Note:
Some other functions may occupy the high nibble of the registers. Altering any
content in high nibble will be undesired.