Rev. 1.00
66
September 11, 2018
Rev. 1.00
67
September 11, 2018
HT45F4050
A/D NFC Flash MCU
HT45F4050
A/D NFC Flash MCU
Pull-high Resistors
Many product applications require pull-high resistors for their switch inputs usually requiring the
use of an external resistor. To eliminate the need for these external resistors, all I/O pins, when
configured as an input have the capability of being connected to an internal pull-high resistor. These
pull-high resistors are selected using the relevant pull-high control registers PAPU~PFPU and
LV
PUC and are implemented using weak PMOS transistors.
Note that the pull-high resistor can
be controlled by the relevant pull-high control registers only when the pin-shared functional pin is
selected as a logic input or NMOS output. Otherwise, the pull-high resistors can not be enabled.
• PxPU Register
Bit
7
6
5
4
3
2
1
0
Name
PxPU7
PxPU6
PxPU5
PxPU4
PxPU3
PxPU2
PxPU1
PxPU0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
POR
0
0
0
0
0
0
0
0
PxPUn
: I/O Px
.n
Pin pull-high function control
0: Disable
1: Enable
The PxPUn bit is used to control the Px
.n
pin pull-high function. Here the "x" can be A, B, C, D, E
and F. However, the actual available bits for each I/O Port may be different.
• LVPUC Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
—
LVPU
R/W
—
—
—
—
—
—
—
R/W
POR
—
—
—
—
—
—
—
0
Bit 7~1
Unimplemented, read as "0"
Bit 0
LVPU
: Low Voltage pull-high resistor c
ontrol
0: All pin pull-high resistors are 30kΩ
@ 5V
1: All pin pull-high resistors are 7.5kΩ
@ 5V
Note that as the pull high resistors are formed using long PMOS transistors, lower
operating voltages will result in higher pull high resistor impedances. It is therefore
recommended that for lower voltage applications the lower pull high resistor value is
chosen.
Port A Wake-up
The HALT instruction forces the microcontroller into the SLEEP or IDLE Modes which preserves
power, a feature that is important for battery and other low-power applications. Various methods
exist to wake-up the microcontroller, one of which is to change the logic condition on one of the Port
A pins from high to low. This function is especially suitable for applications that can be woken up
via external switches. Each pin on Port A can be selected individually to have this wake-up feature
using the PAWU register. Note that the wake-up function can be controlled by the wake-up control
registers only when the pin-shared functional pin is selected as general purpose input/output and the
MCU enters the Power down mode.