Datasheet

Section 8 I/O Ports
Rev. 3.00 Mar 21, 2006 page 179 of 788
REJ09B0300-0300
8.4 Port 3
Port 3 is an 8-bit I/O port. Port 3 pins also function as a bidirectional data bus, XBS bidirectional
data bus, and LPC input/output pins. Port 3 functions change according to the operating mode.
Port 3 has the following registers.
• Port 3 data direction register (P3DDR)
• Port 3 data register (P3DR)
• Port 3 pull-up MOS control register (P3PCR)
8.4.1 Port 3 Data Direction Register (P3DDR)
P3DDR specifies input or output for the pins of port 3 on a bit-by-bit basis.
Bit Bit Name Initial Value R/W Description
7 P37DDR 0 W
6 P36DDR 0 W
5 P35DDR 0 W
4 P34DDR 0 W
3 P33DDR 0 W
2 P32DDR 0 W
1 P31DDR 0 W
0 P30DDR 0 W
Modes 1, 2, and 3 (EXPE = 1)
The input/output direction specified by P3DDR is
ignored, and pins automatically function as data
I/O pins.
Modes 2 and 3 (EXPE = 0)
The corresponding port 3 pins are output ports
when P3DDR bits are set to 1, and input ports
when cleared to 0.