
UM10800
All information provided in this document is subject to legal disclaimers.
© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
78 of 487
NXP Semiconductors
UM10800
Chapter 7: LPC82x Switch matrix (SWM)
GPIOs are special fixed-pin functions. Each GPIO is assigned to one and only one
external pin by default. External pins are therefore identified by their fixed-pin GPIO
function. The level on a digital input is always reflected in the GPIO port register and in the
pin interrupt/pattern match state, if selected, regardless of which (digital) function is
assigned to the pin through the switch matrix.
Remark:
From all movable and fixed-pin functions, you can assign multiple functions to
the same pin but no more than one output or bidirectional function (see
). Use the
following guidelines when assigning pins:
•
It is allowed to connect one input signal on a pin to multiple internal inputs by
programming the same pin number in more than one PINASSIGN register.
Example:
You can enable the CLKIN input in the PINENABLE0 register on pin PIO0_1 and also
assign one ore more SCT inputs to pin PIO0_1 through the PINASSIGN registers to
feed the CLKIN into the SCT.
You can send the input on one pin to all SCT inputs to use as an SCT abort signal.
•
It is allowed to let one digital output function control one or more digital inputs by
programming the same pin number in the PINASSIGN register bit fields for the output
and inputs.
Example:
You can loop back the USART transmit output to the receive input by assigning the
same pin number to Un_RXD and Un_TXD.
•
It is not allowed to connect more than one output or bidirectional function to a pin.
Fig 9.
Functional diagram of the switch matrix
GPIO
PIO0_m
SYSCON
PINTSEL[7:0]
PIN
INTERRUPT
SWM
IOCON
USART0
ANALOG
PERIPHERAL
DIGITAL
PERIPHERAL
DIGITAL
PERIPHERAL
PIO0_m
DIGITAL PAD
ANALOG PAD
digital input
digital output
digital output ena
analog ena
analog i/o
package
pin x
U0_RXD
U0_CTS
U0_SCLK
U0_TXD
U0_RTS
GPIO_INT_BMAT