This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74HC595: There is unexpected signal during transfer

Part Number: SN74HC595

Dear expert,

My customer use 3pcs SN74HC595 in series. IC1's Q7' working as IC2's DS SER. Likewise, IC2's Q7' working as IC3's SER.

The normal waveform was shown below: CH1: SRCLK CH2:RCLK CH3:SER of IC1. CH4: SER of IC2.

Abnormal waveform:CH1: SRCLK CH2:SER of IC1. CH3:SER of IC2. CH4: Output of IC2 

By comparing the waveforms of channels 1, 3, and 4, when the data input of the No. 2 chip corresponds to a low level, its corresponding output pin outputs a high level, causing subsequent circuit malfunctions. Please kindly help check what causes it, thank you!