CMS32L051 User Manual |Chapter 2 Pin Function
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2.3.5 Pull-up resistor selection register (PUxx)
Selection register for internal pull-up resistors. The internal pull-up resistor can only be used in bits for bits
specified by the pull-up resistor select register using the pin using the internal pull-up resistor and the POMmn
bit is 0 and set to input mode (PMmn=1). For bits set to output mode, independent of the setting of the pull-up
resistor selection register, the internal pull-up resistor is not connected. The same is true when used as the
output pin for the multiplexing function or when set to an analog function.
After the reset signal is generated, the pull-up function of the four ports P10, P26, P40, and P137 is turned
on by default (PU10, PU26, PU40, PU137 Reset Value is 1), and the pull-up function of other ports is not
turned on by default.
Register address = base address + offset address; the base address of the PU register is 0x40040000, and
the offset address is shown in the figure below.
Figure 2-5 Format of pull-up resistor selection register
Note 1. The initial value must be set for the unassigned bits.
Note 2. It is limited to CMS32L051xx-S series products. For products other than the CMS32L051xx-S series, ports P60 and
P61 do not have pull-up and pull-down functions of their own and must be used with external pull-up resistors.
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