In the olden days of Intel making CPLDs which, basically were 8 22v10s in a package (forgot part number), I was tasked with driving a very expensive unit in ways that surpased the capabilities of the boards on that 100 line bus. To avoid copyright infringements etc I were blocked off even seeing any proprietary information on the unit I were to interface to.
I made this humongeous board with, I recall, 12 of the Intel devices 100s of "nuggets" and a '51. I configured the CPLDs, the "nuggets" and the processor to work as a logic analyzer and stuffed it into an empty slot on the 100 line bus. The logic analyzer did the signal pickup in the CPLDs and transferred them through a FIFO (4kbyte if I recall) to the '51 which communicated with the PC. The final processing was done in the PC.

This logic analyzer worked beautifully. Eventually I had enough information to reconfigure the same board to drive the unit

conclusion:
If you want a meaningful "logical analysis" you need a VERY fast "front end" such as a CPLD, maybe today you can get there/close with one of the 100MHz SILabs chips.

Erik

PS in my opinion logical analyzers are grossly overrated except in cases as the above. Were I to need a LA today, I would rent it for a week. I guess that once or twice a year I could save a few hours by having one, is that worth the cost of buying one. Really, had I the thousands it cost to buy one, I think i would spend them upgrading my scope. Vignesh, when talking "cost" do not fall in the trap of calculation component cost, your time is (hopefully) worth something too.

If you are absolutotally c ertain that you need a LA, then find the Jack Ganssle article in Embedded Computing magazine where he evaluates the cheap LAs available and buy one. There is no way you can beat $200 if your time is worth anything. These low cost PC based units will be equal or better than anything you can make yourself.