UM10850
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2016. All rights reserved.
User manual
Rev. 2.4 — 13 September 2016
90 of 464
NXP Semiconductors
UM10850
Chapter 7: LPC5410x I/O pin configuration (IOCON)
7.4.2.6 Input filter
Some pins include a filter that can be selectively disabled by setting the FILTEROFF bit.
The filter suppresses input pulses smaller than about 10 ns.
7.4.2.7 Output slew rate
The SLEW bits of digital outputs that do not need to switch state very quickly should be
set to “standard”. This setting allows multiple outputs to switch simultaneously without
noticeably degrading the power/ground distribution of the device, and has only a small
effect on signal transition time. This is particularly important if analog accuracy is
significant to the application. See the relevant specific device data sheet for more details.
7.4.2.8 I
2
C modes
Pins that support I
2
C with specialized pad electronics (P0[23] through P0[28]) have
additional configuration bits. These have multiple configurations to support I
2
C variants.
These are not hard-wired so that the pins can be more easily used for non-I
2
C functions.
See
for recommended mode settings.
For non-I
2
C operation, these pins remain open-drain and can only drive low, regardless of
how I2CSLEW and I2CDRIVE are set. They would typically be used with an external
pull-up resistor if they are used as outputs unless they are used only to sink current.
Leave I2CSLEW = 1, I2CDRIVE = 0, and I2CFILTER = 0 to maximize compatibility with
other GPIO pins.
7.4.2.9 Open-Drain Mode
When output is selected, either by selecting a special function in the FUNC field, or by
selecting the GPIO function for a pin having a 1 in the related bit of that port’s DIR register,
a 1 in the OD bit selects open-drain operation, that is, a 1 disables the high-drive
transistor. This option has no effect on the primary I
2
C pins. Note that the properties of a
pin in this simulated open-drain mode are somewhat different than those of a true open
drain output.