Datasheet

UM10398 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
User manual Rev. 12.3 — 10 June 2014 107 of 547
NXP Semiconductors
UM10398
Chapter 8: LPC1100XL series: I/O configuration (IOCONFIG)
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.
8.3.3 Hysteresis
The input buffer for digital functions can be configured with hysteresis or as plain buffer
through the IOCON registers (see the LPC1100XL data sheet for details).
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.
8.3.4 A/D-mode
In A/D-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 A/D mode is selected, Hysteresis and Pin mode
settings have no effect.
For pins without analog functions, the A/D-mode setting has no effect.
8.3.5 I
2
C mode
If the I
2
C function is selected by the FUNC bits of registers IOCON_PIO0_4 (Table 116)
and IOCON_PIO0_5 (Table 117
), then the I
2
C-bus pins can be configured for different
I
2
C-modes:
• Standard mode/Fast-mode I
2
C with input glitch filter (this includes an open-drain
output according to the I
2
C-bus specification).
• Fast-mode Plus with input glitch filter (this includes an open-drain output according to
the I
2
C-bus specification). In this mode, the pins function as high-current sinks.
• Standard open-drain I/O 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.
8.3.6 Open-drain Mode
When output is selected, either by selecting a special function in the FUNC field, or by
selecting GPIO function for a pin having a 1 in its GPIODIR 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.
8.4 Register description
The I/O configuration registers control the PIO port pins, the inputs and outputs of all
peripherals and functional blocks, the I
2
C-bus pins, and the ADC input pins.
Each port pin PIOn_m has one IOCON register assigned to control the pin’s function and
electrical characteristics.