CMS32L051 User Manual |Chapter 12 Universal Serial Communication Unit
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12.3.16 Registers controlling the function of the serial input/output pin port
When using a general-purpose serial communication unit, the control registers for the multiplexed port
function (Port Mode Register (PMxx), Port Multiplexing Function Configuration Register (PxxCFG), Port Output
Mode Register (POMxx), and Port Mode Control Register must be set (PMCxx)).
For details, please refer to Chapter 2 Pin Functions.
When using the multiplexed port of the serial data output pin or the serial clock output pin as the serial
data output or serial clock output, the bits of the corresponding port mode control register (PMCxx) and the bit
of the port mode register (PMxx) corresponding to each port are 0. In this case, the bit of the port register
(Pxx) can be 0 or 1.
In addition, when used for N-channel open-drain output mode, the bit of the port output mode register
(POMxx) corresponding to each port must be 1.
When using the multiplexed port of the serial data input pin or serial clock input pin as serial data input or
serial clock input, you must set the bit of the Port Mode Register (PMxx) corresponding to each port to "1" and
set the bit of the Port Mode Control Register (PMCxx) to "0". In this case, the Port Register (Pxx) bits can be "0"
or "1".
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