The two display modes of full-color LED display are as follows:

(1)Static display mode

The so-called static display means that when the full-color LED display screen displays a certain character, the corresponding light-emitting diode will appear in two forms: constant on or constant off. This display method requires that the common terminal of each display block is constantly grounded (common cathode) or connected to a positive power supply (common anode). The 8 segment selection lines of each display block are respectively connected to the 8-bit port lines of an 8-bit parallel I/O port. As long as the I/O port has a segment code output, the corresponding characters will be designated and will remain small until I/O outputs new segment code.

When we use a static display mode, we can get high brightness with a smaller current, and it takes up less CPU time and is easy to program. However, since each LED display requires It is equipped with a parallel output port, which takes up a lot of I/O port resources. As a result, its hardware cost becomes high, so it is best not to use this method when there are many display digits.

(2)Dynamic display mode

As for the dynamic display method, it lights up the displays one by one in turn. This method of lighting up the displays one by one is called bit scanning. This display method requires that the segment selection lines of each display are connected in parallel and are mainly controlled by an 8-bit I/O port; while the bit selection lines of each display are controlled by another I/O port line. When displaying in this method, each monitor takes turns to be gated. To enable stable display, the scanning method must be used. That is to say, at a certain moment, we only gate one monitor and send the corresponding segment code, carry out appropriate delay (probably the delay time is about 1-5ms), and then strobe another display, and the corresponding segment code will be sent. If this cycle is repeated, the full-color LED display can be made. Each monitor on the screen displays the corresponding characters. If we can ensure that the cycle time is short enough, we can use the persistence of vision effect of the human eye to give people a display feeling.

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