I/O Lines Programming Example

The programming example shown in the following table is used to obtain the following configuration:

4-bit output port on I/O lines 0 to 3 (should be written in a single write operation), open-drain, with pullup resistor
Four output signals on I/O lines 4 to 7 (to drive LEDs for example), driven high and low, no pullup resistor, no pulldown resistor
Four input signals on I/O lines 8 to 11 (to read push-button states for example), with pullup resistors, glitch filters and input change interrupts
Four input signals on I/O line 12 to 15 to read an external device status (polled, thus no input change interrupt), no pullup resistor, no glitch filter
I/O lines 16 to 19 assigned to peripheral A functions with pullup resistor
I/O lines 20 to 23 assigned to peripheral B functions with pulldown resistor
I/O lines 24 to 27 assigned to peripheral C with input change interrupt, no pullup resistor and no pulldown resistor

I/O lines 28 to 31 assigned to peripheral D, no pullup resistor and no pulldown resistor