Based on the Control Register value only, GPIO Expander Operation state ( input, output, polarity inversion, or configuration ) will set.
But Before Programming, What will be the Value in the Control Register ?
Simply asking What is its default state ?
Kindly Help me on this.
Hello Suriya,
When the part is initially turned on the input, output, polarity inversion, or configuration registers have a default start up state.
The tables above in the far right column show what the default values are upon start up. For example, from the configuration Port0 and 1 registers, we see all ports are defined as inputs shown by 1111 1111. This means upon state up and reset, the ports will always be defined as inputs until you write to these registers.
I am unsure what the values in the control register actually is upon start up but the output, polarity inversion, or configuration registers are already predefined on start up and won't change until you write to them.
The input registers 0 and 1 will be defined by what is on the port pins. Ex. if you have a pull up resistor on all the port pins, then upon start up the input port 0 and 1 registers will all be 1. If left floating the value will be random.
I hope this helps,
-Bobby
