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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
402 of 1441
NXP Semiconductors
UM10503
Chapter 17: LPC43xx/LPC43Sxx System Control Unit (SCU)/ IO
17.3 General description
The system control unit determines the function and electrical mode of most digital pins.
By default, the digital function 0 with pull-up enabled is selected for all pins .
Remark:
Some pins support pin muxing of digital and analog functions. All analog I/Os for
the ADC and DAC are also pinned out on analog-only pads without pin muxing.
17.3.1 Digital pin function
The FUNC bits in the SFS registers control the function of each pin. Each pin can support
up to eight digital functions. Some pins support an additional analog function. If the
function is GPIO, the DIR registers determine whether the pin is configured as an input or
output (see
). For any peripheral function, the pin direction is controlled
automatically depending on the pin’s functionality. The GPIO DIR registers do not affect
peripheral functions.
Table 189. SCU clocking and power control
Base clock
Branch clock
Operating frequency
Clock to SCU register interface
BASE_M4_CLK
CLK_M4_SCU
up to 204 MHz
Fig 43. Block diagram of the I/O pad
slew rate bit EHS
pull-up enable bit EPUN
pull-down enable bit EPD
glitch
filter
analog I/O
ESD
ESD
PIN
VDDIO
VSSIO
input buffer enable bit EZI
filter select bit ZIF
data input to core
data output from core
enable output driver