Question

I have been given the following bit of code as an example:

Make port 0 bits 0-2 outputs, other to be inputs.

FIO0DIR = 0x00000007;

Set P0.0, P0.1, P0.2 all low (0)

FIO0CLR = 0x00000007;

I have been told that the port has 31 LED’s attached to it. I cant understand why, to enable the first 3 outputs, it is 0x00000007 not 0x00000003?

Answer 1

These GPIO config registers are bitmaps.

Use your Windows calculator to convert the hex to binary:

0x00000007 = 111, or with 32 bits – 00000000000000000000000000000111 // three outputs

0x00000003 = 11, or with 32 bits – 00000000000000000000000000000011 // only two outputs