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UM10601
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
102 of 313
NXP Semiconductors
UM10601
Chapter 9: LPC800 Switch matrix
•
If you want to assign a GPIO pin to a pin on any LPC800 package, disable any special
function available on this pin in the PINENABLE0 register and do not assign any
movable function to it.
By default, all pins except pins PIO0_2, PIO0_3, and PIO0_5 are assigned to GPIO.
•
For all other functions that are not in the table of movable functions, do the following:
a. Locate the function in the pin description table in the data sheet. This shows the
package pin for this function.
b. Enable the function in the PINENABLE0 register. All other possible functions on
this pins are now disabled.
9.4 General description
The switch matrix connects internal signals (functions) to external pins. Functions are
signals coming from or going to a single pin on the package and coming from or going to
an on-chip peripheral block. Examples of functions are the GPIOs, the UART transmit
output (TXD), or the clock output CLKOUT. Many peripherals have several functions that
must be connected to external pins.
On the LPC800, most functions can be assigned through the switch matrix to any external
pin that is not a power or ground pin. These functions are called movable functions.
A few functions like the crystal oscillator pins (XTALIN/XTALOUT) or the analog
comparator inputs can only be assigned to one particular external pin with the appropriate
electrical characteristics. These functions are called fixed-pin functions. If a fixed-pin
function is not used, it can be replaced by any other movable function.
GPIOs are fixed-pin functions. Each GPIO is assigned to one and only one external pin.
By default, all external pins have the GPIO function assigned. External pins are therefore
identified by their fixed-pin GPIO function.
9.4.1 Movable functions
Table 94.
Movable functions (assign to pins PIO0_0 to PIO_17 through switch matrix)
Function name
Type
Description
SWM Pin assign
register
Reference
U0_TXD
O
Transmitter output for USART0.
PINASSIGN0
U0_RXD
I
Receiver input for USART0.
PINASSIGN0
U0_RTS
O
Request To Send output for USART0.
PINASSIGN0
U0_CTS
I
Clear To Send input for USART0.
PINASSIGN0
U0_SCLK
I/O
Serial clock input/output for USART0 in synchronous
mode.
PINASSIGN1
U1_TXD
O
Transmitter output for USART1.
PINASSIGN1
U1_RXD
I
Receiver input for USART1.
PINASSIGN1
U1_RTS
O
Request To Send output for USART1.
PINASSIGN1
U1_CTS
I
Clear To Send input for USART1.
PINASSIGN2
U1_SCLK
I/O
Serial clock input/output for USART1 in synchronous
mode.
PINASSIGN2
U2_TXD
O
Transmitter output for USART2.
PINASSIGN2