Something

unsigned char foo;

switch (foo) {
	case 0xAA: do stuff; break;
	case 0xAB: do stuff; break;
}

switch (foo & 0xF0) {
	case 0xA {
		switch (foo & 0x0F) {
			case 0xA: do stuff; break;
			case 0xB: do stuff; break;
		}
		break;
	}
}