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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
76 of 571
NXP Semiconductors
UM10316
Chapter 6: LPC29xx System Control Unit (SCU)
[1]
These bits control the input section of the I/O buffer. The FUNC_SEL bits will define if a pin is input or
output depending on the function selected. For GPIO mode the direction is controlled by the direction
register, see
. Note that input pad type must be set correctly in addition to the FUNC_SEL bits
also for functions of type input.
[2]
The reset value for port pins P0[23:8] is 001 (digital input without internal pull-up/down). This guarantees
that the ADC pins are 5 V tolerant after reset even though the analog pad of ADC1 and ADC2 is not 5 V
tolerant.
[3]
The ‘analog’ connection towards the ADC is always enabled. Use PAD_TYPE = 000 when used as analog
input to avoid the input buffer oscillating on slow analog-signal transitions or noise. The digital input buffer is
switched off.
[4]
When pull-up is activated the input is
not
5 V -tolerant.
[5]
Each pin has up to four functions.
Setting the FUNC_SEL bits in the SFSP5_16 register also determines the function of port
5[17]. If the USB_D
−
2 function is selected for P5[16], P5[17] is automatically assigned to
the USB_D+2 function. If P5[16] is GPIO, P5[17] is assigned to GPIO as well.
Setting the FUNC_SEL bits in the SFSP5_18 register also determines the function of port
5[19]. If the USB_D
−
1 function is selected for P5[18], P5[19] is automatically assigned to
the USB_D+1 function. If P5[18] is selected GPIO, P5[19] is assigned to GPIO as well.
1 to 0
FUNC_SEL[1:0]
R/W
Function-select; for the function-to-port-pin
mapping tables
00*
Select pin function 0
01
Select pin function 1
10
Select pin function 2
11
Select pin function 3
Table 59.
SFSP5_16 function select register bit description (SFSP5_16, address
0xE000 1540)
Bit
Symbol
Access
Value
Description
31 to 2
reserved
R
-
Reserved. Read as
logic 0
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[16]
01
Select pin USB_D
−
2
10
reserved
11
reserved
Table 58.
SFSPn_m register bit description (base address: 0xE000 1000 (port 0), 0xE000
1100 (port 1), 0xE000 1200 (port 2), 0xE000 1300 (port3), 0xE000 1400 (port4),
0xE000 1500 (port 5))
…continued
* = reset value
Bit
Symbol
Access
Value
Description