UM10462
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 5.5 — 21 December 2016
82 of 523
NXP Semiconductors
UM10462
Chapter 7: LPC11U3x/2x/1x I/O configuration
not applicable to the Deep power-down mode. Repeater mode may typically be used to
prevent a pin from floating (and potentially using significant power if it floats to an
indeterminate state) if it is temporarily not driven.
7.3.3 Hysteresis
The input buffer for digital functions can be configured with hysteresis or as plain buffer
through the IOCON registers.
If the external pad supply voltage V
DD
is between 2.5 V and 3.6 V, the hysteresis buffer
can be enabled or disabled. If V
DD
is below 2.5 V, the hysteresis buffer must be
disabled
to use the pin in input mode.
7.3.4 Input inverter
If the input inverter is enabled, a HIGH pin level is inverted to 0 and a LOW pin level is
inverted to 1.
7.3.5 Input glitch filter
Selected pins (pins PIO0_22, PIO0_23, and PIO0_11 to PIO0_16) provide the option of
turning on or off a 10 ns input glitch filter. The glitch filter is turned on by default. The
RESET pin has a 20 ns glitch filter (not configurable).
7.3.6 Open-drain mode
A pseudo open-drain mode can be supported for all digital pins. Note that except for the
I
2
C-bus pins, this is not a true open-drain mode.
7.3.7 Analog mode
In analog mode, the digital receiver is disconnected to obtain an accurate input voltage for
analog-to-digital conversions. This mode can be selected in those IOCON registers that
control pins with an analog function. If analog mode is selected, hysteresis, pin mode,
inverter, glitch filter, and open-drain settings have no effect.
For pins without analog functions, the analog mode setting has no effect.
7.3.8 I
2
C mode
If the I
2
C function is selected by the FUNC bits of registers PIO0_4 (
) and PIO0_5
(
), then the I
2
C-bus pins can be configured for different I
2
C-modes:
•
Standard mode/Fast-mode I
2
C with 50 ns input glitch filter. An open-drain output
according to the I
2
C-bus specification can be configured separately.
•
Fast-mode Plus I
2
C with 50 ns input glitch filter. In this mode, the pins function as
high-current sinks. An open-drain output according to the I
2
C-bus specification can be
configured separately.
•
Standard functionality without input filter.
Remark:
Either Standard mode/Fast-mode I
2
C or Standard I/O functionality should be
selected if the pin is used as GPIO pin.