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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
77 of 571
NXP Semiconductors
UM10316
Chapter 6: LPC29xx System Control Unit (SCU)
3.1.1 Functional description
The digital I/O pins of the device are divided into four ports. For each pin of these ports
one out of four functions can be chosen. Refer to
for a schematic
representation of an I/O-pin. The I/O functionality is dependent on the application.
The function of an I/O can be changed ‘on the fly’ during run-time. By default it is assigned
to function 0, which is the GPIO. For each pin of these ports a programmable pull-up and
pull-down resistor (R) is present.
Remark:
Even though the default function is GPIO, the pad type has to be set to digital in
the SFSPn_m registers in order to use the GPIO functionality (see
Table 60.
SFSP5_18 function select register bit description (SFSP_5_18, address
0xE000 1548)
Bit
Symbol
Access
Value
Description
31:5
-
-
-
reserved
4
VBUS
R/W
<tbd>
0
port 1 in host or device
mode
1
port 1 in OTG mode
3 to 2
-
-
-
reserved
1 to 0
FUNC_SEL[1:0]
R/W
Function-select; for the
function-to-port-pin mapping
tables
00*
Select pin function GPIO on
P5[18]
01
Select pin USB_D
−
1
10
reserved
11
reserved
Fig 15. Schematic representation of an I/O pin
R
R
SFSPx_y
FUNC_SEL
RESERVED
Function 3
Function 0
Function 1
Function 2
Vdd
Vss
Vss
PAD_TYPE