Simple question, i need to use 3 shift register to control 6 analog switches and 12 leds with only 6 digital outputs, nothing difficult BUT my IC provider doesnt have the clasic 595 in DIP package, so i was wondering to use a 594. Because i'm using analog switches for analog signals, it is very important that they all change at the same time, 595 has latch outputs with OE, wich is perfect, 594 just has a Rclk to pass with a pulse the data from Shift Registers to Out Registers, so my question exactly is :

Can i use ONLY this Rclk to control each IC (1 for analog switches and 2 for the leds) that way i put all the Shift Reg clk together so data goes thru all 3 IC and the Reg clr also together cause i need to have a LOW output everywhere at the power on of the system. SO : 6 outs pins from microcontroller = 3xRclk, Serial data, Sr clk, Reg clr (Sr clr are put to high)


  • \$\begingroup\$ You can buy it here digikey.com/product-detail/en/texas-instruments/SN74HC595N/… \$\endgroup\$
    – Leoman12
    May 4, 2020 at 2:09
  • \$\begingroup\$ Thanks, but i'm in europe, have a profesional acount at "Farnell", they only have the 595 in SOIC package, but i'm only prototyping for now so i need DIP package, maybe later i'll go to SMD \$\endgroup\$ May 4, 2020 at 9:14

1 Answer 1


If you don't need the /OE (tri-state) functionality of the HC595, the HC594 is almost equivalent, except for the /RCLR input (which the HC594 has and the HC595 does not have). Pinouts, except for the /OE and /RCLR pins mentioned, are nearly the same.


The setup you descibe would work for 3 cascaded 594s with individual RCLKs. As you have to shift in 24 new bits whenever 1 output changes anyway, you could ask yourself if you need 3 separate RCLKs (one might do).

The same goes for /RCLR on the HC594. A parallel reset is very handy if you can spare an I/O pin on the Arduino, but you accomplish the same by shifting in 24 zeroes on startup (which you would have to do if you had a HC595 anyway).

  • \$\begingroup\$ Hello StarCat, thanks this is a great answer, actually the question was if i need to shift all 24 bits everytime i change anything, so yes then i dont need individual RCLKs. \$\endgroup\$ May 4, 2020 at 10:40
  • \$\begingroup\$ Parts are ordered, i'll inform how it will go, again thanks ! \$\endgroup\$ May 4, 2020 at 10:40

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