
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 8: General Purpose Input Output Pins
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
8-4
The GPIO pins are controlled by software through MMIO register reads and writes.
The MMIO registers allow to control the operating mode of the GPIO pin (on a pin-by-
pin basis) but also set its value or read its value.
2.1.1
GPIO Mode settings
Each GPIO pin operates in 1 of 3 following modes:
primary function
open drain output
tri-state output.
There are four GPIO Mode Control registers allocated to control the operating mode
of the 61 PNX15xx Series GPIO pins. Each pin uses a 2-bit mode eld located in one
of the 4 Mode Control registers. Register MC0 controls GPIO pins [15:0], MC1
controls pins [31:16], etc. The 2-bit control values function is described in
Table 2.
2.1.2
GPIO Data Settings MMIO Registers
When a pin is set for GPIO mode, the data can be read and written by accessing one
of four MASK and I/O Data (IOD) registers. Each of these registers accesses 16 of
the 61 GPIO signals. Each register is composed of 16 MASK bits and 16 IOD bits.
The MASK and IOD eld make up a 2-bit value: the MASK bit is located in the upper
16 bits (31:16) and the IOD bit is located in the lower 16 bits (15:0) of the
corresponding 32-bit MMIO register (groups 16 GPIO pins). For example, MASK
Figure 2:
Functional Block Diagram of a GPIO Pin
OEN
PIN
PAD INPUT
PAD OUTPUT
GPIO
ANY
MODULE
FUNCTIONAL
INPUT
MODULE
FUNCTIONAL
OUTPUT
Disabling
Logic
GPIO
Muxing
GPIO
Logic
MODULE
FUNCTIONAL
OUTPUTE ENABLE
(OEN)
Table 2: GPIO Mode Select
GPIO
Mode
Description
00
Retain pin mode of operation. A write with this mode does not overwrite current
mode.
01
Switch pin mode to primary operating mode.
10
Switch pin mode to GPIO mode.
11
Switch pin mode to open-drain GPIO (this prevents active high drive).