Timer with ABCD comparator

Question

Dear Team , 
 I have a concern regarding the ABCD comparator and timer with stop start and reset control on Sigma Studio GUI 
 I am trying to compare two sine waves ,one with some decay and the other with a normal fixed amplitude for the entire length of time. 
 After I feed these two inputs to an ABCD conparator,I would like the output of the Comparator to send a 1 until and unless the sample value in pin a is less than sample value in pin b but once the reverse happens I would want the timer to be stopped by the 0 output of the Comparator and hence stop counting any further samples once the decay is over . However I am not getting fruitful results . 
 Can anyone help

Ken.M · Accepted Answer

You have opened a couple of posts of posts so I will do my best to answer them both here. Bob (not an ADI employee) was kind enough to send an example project. Did that provide any guidance? As I said, I am not able to comment on your project without more information. There are lots of ways that you may have tried to implement this. Please post the project(s) that you have created so far, and I will try to guide you. 
 It appears that you are interested in tracking the envelopes of signals rather than the instantaneous values. You will need to use an envelope detector to do this effectively. It does not sound like you have implemented this advice. Even with the tones in phase (same oscillator), if you are passing the signal through a volume control with slew, it is entirely possible that the signal with gain is remaining one LSB or more below the direct signal. I would recommend that you add a small constant before the comparison to provide a little hysteresis. Try replacing the slewed volume control with a gain block that you can better control numerically. A gain of 1 in the gain cell should give the exact same signal. 
 Readback cells do not provide instantaneous values of variables. They are literally "read back" from the DSP to the SigmaStudio GUI by polling the SPI (or I2C) port with the USBi. Since this polling is statistical, you are unlikely to catch the exact peak of a sine tone, for example. 
 I am assuming that your slew questions are only tangentially related to your sample counting question. Details on the hardware slew may be found in this post and downloaded here . The equations for the hardware slew are more rigorous than for software slew. If you need exact time constants, I suggest you take advantage of the hardware. 
 Ken)