595 as Demultiplexer w/ Max

Hi I recently purchased some serial in parallel out 3 stage shift registers (part num 74HC595). I have gotten interesting random results with some simple programing of my arduino (my microcontroller) but the actual function of the three pins data, SH, and ST still elude me. I have researched the web including this site and little scales blog (whose max patch didn't work for me :-/ Do I have it right: Data Pin (pin14): This pin decides the state of each register/bit (high or low) SH_Clock(pin12): This is the clock that simply reads the data pin state every pulse ST_Clock(pin11): Called latch pin, when this goes high all the bits collected and pushed out, creating the parallel effect. This pin is what collects the byte and moves it. Ja?

Thanks again, Max PS these chips are being used as demultiplexers

No. Data Pin 14 - This is the data input, the value here is transferred into the lowest bit of the shift register and all the other bits move up one place when the shift register is clocked. Clock Pin 12 - Cause the bits in the shift register to move up one place on a positive edge. That is when the signal line goes from a zero to a one. Latch Clock Pin 11 - Causes the output of the shift registers to be transferred and held on the output pins when it receives a positive edge (just like the last clock).

So to use it connect all three pins to Arduino outputs. Place the data you want, one bit at a time onto the data input. In between each data bit put the clock low then high. At the end of doing this 8 times take the latch clock high then low. The data outputs Qa to Qh will no contain the data bits you placed on the Data input. Note the first data bit you put to pin 14 will appear on Qh and the last will appear on Qa.

Hope that helps.

Thanks so much. Let me figure this here: ok so the latch pin outputs every Q simulataniosly upon low to high transition? And the shiftclock moves the bit (governed high or low by the data pin) from Q0 up the line to Q7? After the register is full the latch should be then raised high to output all states.


I have gotten the 595 to work with igoes tutorial I just want more info because I want to try and control the register with MSP.

Yes that's it you've got it. :)