Not sure where I am going wrong here. No matter what data I send the shift register all the outputs are high. In the example below I would expect only one output to be high but all are high.

The only way I can get the outputs to go low is to send all zeros in the data.

 

The shift register and the output register operate independently. The procedure is to clock 8 bits of data into the shift register. Then clock 8 bits of data from the shift register to the output register. In this way the transient state of the shift register does not show up in the output register.

You schematic is faulty and misleading because it shows the shift register clock and the parallel output register clock connected together with no driving source. Read datasheets carefully you must -- young Jedi!

Your default assumption must be that the datasheet is correct and the error is one of understanding.

 

Thanks. Yeah I think I got it now. Or at least getting closer. I know have an issue with an output or two not lighting when I expect but need to investigate further

 

OK I modified my circuit to have separate clocks. What I do now is to clock in the 8 bits on SRClock then Clock in te result to the register with RClock. All is working as expected except,


Here where no outputs go high



And here where QF and QE both go high simultaneously.

 

Bad chip. Swapped it out. Working perfectly now!