Analysis of 1/4 scanning circuit of LED display

Circuit Analysis:

1. This circuit is a row selection circuit, which is used to select and drive the corresponding row. The 4953 chip plays the role of amplification.

2. This 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 via the 3-8 decoder, which means that the entire circuit does not have a 3-8 decoder. This circuit uses 4 signal lines, A, B, C, and D, for row selection. When the A signal is valid, 4 rows will be selected. Similarly, when the B, C, and D signals are valid, 4 rows will be selected. Scanning 4 times completes a cycle, so it is a 1/4 scan. To understand the scanning method of this circuit from another angle, the circuit controls a total of 16 rows, and uses 4 signal lines for selection, so 4/16=1/4. Therefore, it is a 4-scan circuit.

3. This circuit shows that it is not necessary to use a 3-8 decoder to realize scanning mode. It is not like many materials say that as long as there are A, B, C, D signals in the interface definition, it is a 16-scan mode. To determine what scanning mode is, look at the A, B, C, D signals and whether there is a 3-8 decoder. If there are A, B, C signals and 1 3-8 decoder, it is a 1/8 scanning mode. If there are A, B, C, D signals and 2 3-8 decoders, it is a 1/16 scanning mode.