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TDC7200: START/STOP Signals - Pulse required?

Klaus Bahner
Prodigy 70 points
Part Number: TDC7200

Hi again,

Provided the config register is set to positive edge trigger for the start/stop signals, is it then required to provide these signals as pulses as for example shown in figure 16 of the datasheet? Or can the been held high after the transition? Of course signals have to return to low before a new measurement can be started - but this is not the issue here. I just want to know whether there is a requirement for the start signal to be low before a low to high transition on the stop signal can be detected.

Assuming start/stop signals are truly edge triggered the signal state after the transition should not matter at all, but the datasheet always shows the start/stop signal return to low within a clock cycle - hence my doubt.

Best regards
Klaus

  • 0
    TI__Genius 11015 points

    Klaus,

    The register CONFIG1 bits 3 & 4 determine the edge polarities for the START & STOP pins. 

    In order to achieve the highest measurement accuracy, having the same edge polarity for the START and STOP input signals is highly recommended. Otherwise, slightly different propagation delays due to symmetry shift between the rising and falling edge configuration will impact the measurement accuracy. For highest measurement accuracy in measurement mode 2, it’s strongly recommended to choose for the START and STOP signal the “rising edge”. This is done by setting the START_EDGE and STOP_EDGE bits in the CONFIG1 register to 0.

    These signals can be held high after the transition from low to high. There is no specific period wherein the START signal needs to be low before the system can detect the STOP.

  • 0 in reply to Bharat Aravamudhan
    Prodigy 70 points

    Thanks a lot for the answer