LPC810M021FN8 datasheet(80/313 Pages) NXP

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UM10601

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Preliminary user manual

Rev. 1.0 — 7 November 2012

80 of 313

NXP Semiconductors

UM10601

Chapter 7: LPC800 GPIO port

7.6.9 GPIO port toggle registers

Output bits can be toggled/inverted/complemented by writing ones to these write-only

registers, regardless of MASK registers.

7.7 Functional description

7.7.1 Reading pin state

Software can read the state of all GPIO pins except those selected for analog input or

output in the “I/O Configuration” logic. A pin does not have to be selected for GPIO in “I/O

Configuration” in order to read its state. There are several ways to read the pin state:

• The state of a single pin can be read with 7 high-order zeros from a Byte Pin register.

• The state of a single pin can be read in all bits of a byte, halfword, or word from a

Word Pin register.

• The state of multiple pins in a port can be read as a byte, halfword, or word from a

PORT register.

• The state of a selected subset of the pins in a port can be read from a Masked Port

(MPORT) register. Pins having a 1 in the port’s Mask register will read as 0 from its

MPORT register.

7.7.2 GPIO output

Each GPIO pin has an output bit in the GPIO block. These output bits are the targets of

write operations “to the pins”. Two conditions must be met in order for a pin’s output bit to

be driven onto the pin:

1. The pin must be selected for GPIO operation in the switch matrix.

2. The pin must be selected for output by a 1 in its port’s DIR register.

If either or both of these conditions is (are) not met, writing to the pin has no effect.

There are multiple ways to change GPIO output bits:

Table 76.

GPIO clear port 0 register (CLR0, address 0xA000 2280) bit description

Bit

Symbol

Description

Reset

value

Access

17:0

CLRP0

Clear output bits:

0 = No operation.

1 = Clear output bit.

31:18

Reserved.

Table 77.

GPIO toggle port 0 register (NOT0, address 0xA000 2300) bit description

Bit

Symbol Description

Reset

value

Access

17:0

NOTP0

Toggle output bits:

0 = no operation.

1 = Toggle output bit.

31:18 -

Reserved.

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