LED display 1/4 scan circuit analysis

4 scan circuit diagram

circuit analysis:

1. This circuit is a row selection circuit that selects and drives the corresponding row. The 4953 chip plays a magnifying role.

2. The circuit is a 1/4 scan circuit. It can be seen that the A, B, C, and D signals from the HC245 chip are not directly connected to the 4953 chip through the 3-8 decoder, indicating that the entire circuit does not have a 3-8 decoder, and the circuit uses A, B, and C. , D a total of 4 signal lines to do the line selection. When the A signal is valid, 4 lines are selected. Similarly, when the B, C, and D signals are valid, 4 lines are selected. Scanning 4 times completes one cycle, so it is 1/4 scan. Change the angle to understand the scanning mode of the circuit. The circuit controls a total of 16 lines, sharing 4 signal lines for selection, so 4/16=1/4. So it is 4 scan circuits.

3, the circuit shows that the implementation of the scanning mode does not have to use a 3-8 decoder. It is not like a lot of information, as long as there are A, B, C, D signals in the interface definition, it is 16 scanning mode. To determine what scanning method is, look at the A, B, C, D signals, but also to see if there is a 3-8 decoder. If there are A, B, C signals, and a 3-8 decoder, it is 1/8 scan mode. If there are A, B, C, D signals and there are 2 3-8 decoders at the same time, it is 1/16 scan.

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