Nxp Semiconductors UM10237 User Manual

UM10237_2

© NXP B.V. 2008. All rights reserved.

 

LPC2400 has up to five 32-bit General Purpose I/O ports. PORT0 and PORT1 are 
controlled via two groups of registers as shown in 

 and 

. Apart 

from them, LPC2400 can have three additional 32-bit ports, PORT2, PORT3 and PORT4. 
Details on a specific GPIO port usage can be found in the chapters "Pin Configuration" 
and "Pin Connect Block".

Legacy registers shown in 

 allow backward compatibility with earlier family 

devices, using existing code. The functions and relative timing of older GPIO 
implementations is preserved. Only PORT0 and PORT1 can be controlled via the legacy 
port registers.

The registers in 

 represent the enhanced GPIO features available on all of 

the LPC2400’s GPIO ports. These registers are located directly on the local bus of the 
CPU for the fastest possible read and write timing. They can be accessed as byte or 
half-word long data, too. A mask register allows access to a group of bits in a single GPIO 
port independently from other bits in the same port.

When PORT0 and PORT1 are used, user must select whether these ports will be 
accessed via registers that provide enhanced features or a legacy set of registers (see 

). While both of a port’s 

fast and legacy GPIO registers are controlling the same physical pins, these two port 
control branches are mutually exclusive and operate independently. For example, 
changing a pin’s output via a fast register will not be observable via the corresponding 
legacy register.

The following text will refer to the legacy GPIO as "the slow" GPIO, while GPIO equipped 
with the enhanced features will be referred as "the fast" GPIO.

P0[31:0]
P1[31:0]
P2[31:0]
P3[31:0]
P4[31:0]

Input/
Output

General purpose input/output. These are typically shared with other 
peripherals functions and will therefore not all be available in an 
application. Packaging options may affect the number of GPIOs 
available in a particular device.

Some pins may be limited by requirements of the alternate functions of 
the pin. For example, the pins containing the I

2

C0 functions are 

open-drain for any function selected on that pin. Details may be found 
in the LPC2400 pin description in