UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
333 of 362
NXP Semiconductors
UM10208
Chapter 26: LPC2800 GPIO
5.
Register description
The 85 potential GPIO pins are designated by port number and pin number within the
port. For instance, pin 5 of port 3 is referred to as P3.5. This notation is also used in the
Event Router chapter. Note, that in the LPC2300 pinning chapter a different notation is
used: P3[5] for P3.5.
5.1 I/O configuration
Each potential GPIO pin has two related register bits that determine whether they are
used as GPIO or as a peripheral function and that control the pin if it is in GPIO mode.
These two bits are corresponding bits in MODE1_n and MODE0_n registers. For
example, P3.5 is controlled by bit 5 of registers MODE1_3 and MODE0_3. The MODE1
register may be thought of as the GPIO output enable, and when enabled, the MODE0
register is the GPIO data value. See
All of these bit pairs reset to the value 01, so that all potential GPIO pins default to the
peripheral function, either input or output depending on the default for the that function.
P5 (6 pins)
MD0 / P5.5 to MD3 /
P5.2
These GPIOs are shared with the SD/MCI data bus.
MCMD / P5.1
This GPIO is shared with the SD/MCI command
output.
MCLK / P5.0
This GPIO is shared with the SD/MCI clock output.
P6 (4 pins)
RTS / P6.3
This GPIO is shared with the UART request to send
output.
CTS / P6.2
This GPIO is shared with the UART clear to send
input.
TXD / P6.1
This GPIO is shared with the UART transmit data
output.
RXD / P6.0
This GPIO is shared with the UART receive data input.
P7 (1 pin)
VBUS / P7.0
This GPIO is shared with the USB voltage sense input.
Table 366. Pin description
Port
Pin(s)
Description
Table 367. m1:0 state vs. pin state
m1
m0
Pin State
0
0
GP in (not driven)
0
1
Peripheral function (input, output, or input/output)
1
0
GP out (driven low)
1
1
GP out (driven high)