• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 20 subscribers
  • Views 733 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74LVC1G373DCKR replacement with know initial state

user4451094
Prodigy 20 points

The support forum indicates that

"On all Flip Flops at power up  the outputs can not be determined unless the part has a clear or preset or after first valid clock."

Is this true for the SN74LVC1G373DCKR part and if so can you recommend a replacement part.

Our design has the OE line tied low but the Latch and Data input are fead directly from the outputs of a K60 processor.

Since the K60 always has the outputs tristate for a short while after power on or software reset we need to ensure the output status of the SN74LVC1G373DCKR is low on power up and also does not change states when it's inputs are again floated if the K60 is software reset.

  • 0
    TI__Guru 62270 points
    Hi ,
    Based on the datasheet , it is true that the output isn't deterministic on startup .This device doesn't have either clock or clr/pre pins .The OE pin can be connected using weak pullup resistor to Vcc to have the outputs Hi-Z mode whenever the processor is still powering on. If you want to ensure your outputs low on reset , I may suggest weak pulldowns on D and weakpullups on LE .
    Sorry ,I couldn't see any devices in the product category of the one you are using right now .
  • 0 in reply to ShreyasRao
    Prodigy 20 points
    Thank You

    Yes I thought of this answer but the Latch also has to maintain its current state while the K60 occasionaly executes a Watch Dog Reset.
    When this happens the D and LE lines will take the state of the weak pulldowns and weakpullups respectively. This will force the latch back to the clear state from whatever state it is in. Unless there is a way to prevent the K60 from tristating during a reset I do not see this working. If the K60 output pins could maintain their drive status during a Watch Dog Reset (as far as I know this is not possible) the resistors alone would work.

    If you have additional suggestions I would appreciate them.

    Corry
  • 0 in reply to user4451094
    TI__Guru 62270 points
    Hi Corry ,
    Tough choice here , not sure what else can be the suggestions based on the limited knowledge on K60 processors you are using . That's unfortunately the way the part works .