题目内容
When. P0 port is used as general I / O port, the external pin must be connected with pull-up resistor, so it is a quasi -bidirectional port.
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When P1-P3 ports are used as input ports, 1 must be written to the port register first.
The driving ability of P0-P3 ports is the same.
When the number of LED display is large, the dynamic display takes up more I / O ports. In order to save the number of I / O ports and driving circuits, the static scanning display mode is often used.
The dynamic scanning display circuit of LED digital tube can cause the false appearance of "multiple LED digital tubes on at the same time" as long as the display time of each digital tube is well controlled, so as to achieve the effect of multiple LED digital tubes on display at the same time.
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