CD4067BE is a BCD latched \/ 7-segment decoder\/driver, commonly used display decoding device, MAX7219 and his function is similar. CD4067BE pin function: BI: 4 pin is the blanking input control terminal, when BI=0, no matter what the state of the other input terminal is, the seven sections of the digital tube will be in the blanking state that is not displayed. LE: Locks the control terminal and allows decoding output when LE=0. When LE=1, the decoder is locked and held, and the decoder output is held at the value of LE=0. LT: 3 pin is the input end of the test signal, when BI=1, LT=0, the decoding output is all 1, regardless of the input DCBA status, all seven segments are illuminated. It is mainly used to detect whether the number 7 code tube has physical damage. A1, A2, A3, A4, are 8421BCD code input terminals. a, b, c, d, e, f, g: is the decoding output terminal, the output is valid for high level 1.