UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
300 of 1269
NXP Semiconductors
UM10503
Chapter 15: LPC43xx System Control Unit (SCU)/ IO configuration
1. Tri-state the output driver by selecting an input at the pinmux e.g. GPIO function in
input mode.
2. Disable the receiver by setting the EZI bit to zero (see
or
the default setting.
3. Disable the pull-up resistor by setting the EPUN bit to one, and disable the pull-down
resistor by setting the EPD bit to zero.
4. Set the bit corresponding to the analog function to 1in the ENAIO2 register.
15.4.8.1 Measuring the band gap
To measure the band gap, set up the pin configuration and ADC function select registers
for pin PF_7 as follows:
1. Disable the pull-up and the input buffer: Set register SFSPF_7 at 0x4008 679C to
0x10.
2. Connect the ADC1_7 input to the digital pad: Set register ENAIO1at 0x4008 6C8C to
0x80.
3. Connect the band gap to the digital pad: Set register ENAIO2 at 0x4008 6C90 to
0x10.
4. Do not connect pin PF_7 on the board.
15.4.9 EMC clock delay register
This register provides a programmable delay for the EMC clock outputs. The delay for all
EMC_CLKn clock outputs is the same and increases in approximately 0.5 ns steps from 0
(CLK_DELAY = 0 to 3.5 ns (CLK_DELAY = 0x7777). The exact values of the delays vary
over temperature and processing.
Table 143. Analog function select register (ENAIO2, address 0x4008 6C90) bit description
Bit
Symbol
Value Description
Reset
value
Access
0
DAC
Select DAC
0
R/W
0
Digital function selected on pin P4_4.
1
Analog function DAC selected on pin P4_4.
3:1
Reserved
-
-
4
BG
Select band gap output. To measure the band gap,
disable the pull-up on pin PF_7 and connect PF_7
to the digital pad. Do not use the digital pad nor the
ADC1_7 on the board when measuring the band
gap (see
).
0
R/W
0
Digital function selected on pin PF_7.
1
Band gap output selected for pin PF_7.
31:5
Reserved
-
-