UM11029
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User manual
Rev. 1.0 — 16 June 2017
208 of 515
NXP Semiconductors
UM11029
Chapter 12: LPC84x General Purpose I/O (GPIO)
12.5.2 GPIO port word pin registers
Each GPIO pin has a word register in this address range. Any byte, halfword, or word read
in this range will be all zeros if the pin is low or all ones if the pin is high, regardless of
direction, masking, or alternate function, except that pins configured as analog I/O always
read as zeros. Any write will clear the pin’s output bit if the value written is all zeros, else it
will set the pin’s output bit.
12.5.3 GPIO port direction registers
Each GPIO port has one direction register for configuring the port pins as inputs or
outputs.
Table 255. GPIO port byte pin registers (B[0:53], addresses 0xA000 0000 (B0) to 0xA000 0035
(B53)) bit description
Bit
Symbol Description
Reset
value
Access
0
PBYTE Read: state of the pin PIO0m_n, regardless of direction,
masking, or alternate function, except that pins configured as
analog I/O always read as 0. One register for each port pin:
m = port 0 to 1; n = pin 0 to 31 for port 0, and pin 0 to 21 for
port 1.
Write: loads the pin’s output bit.
ext
R/W
7:1
Reserved (0 on read, ignored on write)
0
-
Table 256. GPIO port word pin registers (W[0:53], addresses 0xA000 1000 (W0) to 0xA000
10D4 (W53)) bit description
Bit
Symbol
Description
Reset
value
Access
31:0
PWORD Read 0: pin PIOm_n is LOW.
Write 0: clear output bit.
Read 0xFFFF FFFF: pin PIOm_n is HIGH.
Write any value 0x0000 0001 to 0xFFFF FFFF: set output
bit.
Remark:
Only 0 or 0xFFFF FFFF can be read. Writing any
value other than 0 will set the output bit.
One register for each port pin: m = port 0 to 1; n = pin 0 to 31
for port 0; n = pin 0 to 21 for port 1.
ext
R/W
Table 257. GPIO direction port register (DIR[0:1], address 0xA000 2000 (DIR0) to
0xA00002004 (DIR1)) bit description
Bit
Symbol
Description
Reset
value
Access
31:0
DIRP
Selects pin direction for pin PIOm_n (bit 0 = PIOm_0, bit 1 =
PIOm_1, ..., bit 31 = PIOm_31). m = port 0 to 1; n = pin 0 to
31 for port 0 and pin 0 to 21 for port 1.
0 = input.
1 = output.
0
R/W
