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SN74LV8154: counter resets of RCLK is connected

Intellectual 480 points

Replies: 3

Views: 78

Part Number: SN74LV8154

Hey, everyone!

I am using SN74LV8154 binary counter with Hercules RM57Lx LaunchPad. It counts but keeps resetting at 15 or 7 (or sometimes less).

After investigating, I observed that when I remove the RCLK connection for a while and then connect it back, the counts' value it shows is more than 15 (e.g. 20-30, 100, 8852, etc.). I checked multiple times. When RCLK is not connected, it counts fine but resets when RCLK is connected.

Please, help!


  • Schematic?

  • In reply to Clemens Ladisch:

    I do not have a clean drawn schematic but the connections are the following:

    (left side is SN74LV8154)

    Y0-Y7 -----  GIOA 0, 1, 2, 5, 6, 7, GIOB 2, 3
    VCC   -----  5V
    GND  -----  GND
    GAL   -----  HET1_2
    GAU  -----  HET1_18
    GBL   -----  HET1_16
    GBU  -----  HET1_30
    CLKA -----  HET1_22
    CLKB -----  (not connected)
    RCLK -----  HET1_14
    CCLR -----  HET1_4
    (RCOA and CLKBEN shorted)

    Please, find the code attached as well.



  • In reply to Apurv Mishra:

    Hi Apurv,

    Your code appears fine. RCLK should not cause the counter to clear,  do you have access to an oscilloscope to see if CCLR is glitching low for some reason when RCLK is connected? Also make sure your delay function is meeting the timing requirements for this device.