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Latch shift register — Parallax Forums

Latch shift register

alnajjar1alnajjar1 Posts: 110
edited 2011-04-06 11:00 in BASIC Stamp
I am using the 74HC595 to power up TIP120 to turn on LED strips (~1A per strip). The 74HC595 can provide 8 ouputs but to my knowledge they can not be "daisy chained" like the 74HC165. Being very tight on pins, is there a cousin to the 74HC595 with 16 or 32 latches?

many thanks in advance,

Al

Comments

  • LeonLeon Posts: 7,620
    edited 2011-04-05 13:04
    They can be daisy-chained.
  • davejamesdavejames Posts: 4,047
    edited 2011-04-05 14:29
    As Leon suggested, the 74HC595 can be daisy-chained. This is done by using the serial in and serial out pins which will allow you to string a whole bunch of 'em together.

    Check out page 8 of this data sheet for some insight: http://www.onsemi.com/pub_link/Collateral/MC74HC595A-D.PDF

    DJ
  • alnajjar1alnajjar1 Posts: 110
    edited 2011-04-05 19:48
    That's good news. How do you communicate with let's say the 2nd or 3rd IC? In other words, if I have 4 of these guys and I want to turn on out7 of the last chip in the chain, what would the shiftOut command look like? I know this may sound elementary for the shiftout expert, but I have never done it

    many thanks again,

    Al
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-04-05 20:45
    Oh, Al; get off the stick.
    http://forums.parallax.com/showthread.php?129022-Program-BS2-and-more-then-three-74HC595-s&highlight=74HC595
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-04-06 09:55
    Why not just answer the stated question/s (an not go "shooting stars" as you say)?
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2011-04-06 10:06
    alnajjar1 wrote: »
    That's good news. How do you communicate with let's say the 2nd or 3rd IC? In other words, if I have 4 of these guys and I want to turn on out7 of the last chip in the chain, what would the shiftOut command look like? I know this may sound elementary for the shiftout expert, but I have never done it

    Once you have them all wired up sending data to more 74HC595 chips is trivial. If you only had one you would shift out the bits 8 times then latch it. If you have two then you'll send 16 bits. Four 74HC595 chips would require you to shift out 32 bits. Once all the bits have been sent to the chips you toggle the latch line. The first 8 bits sent will end up in the last chip connected. The latch and clock pins are common between all the chips. The serial out from your Microcontroller goes to the first chip. The output of the first chip goes to the 2nd and so on.

    Robert
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-04-06 11:00
    I guess grasping at straws is a real sport for the "star shooting" set.
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