Hi Simon,

1) Take a fine CRO and look for the distortions in the waveform
If there is no wave form then you know what to do.

2) If you find distortions then apply appropriate RC filter to
snub the harmonics and then try to detect again ,it is difficult
to get errorfree signals with MT8880,If you look at the
AN you can clearly make out 8880 is not bus compatible with
8051 so why use this chip?.

3) If the things are still worse Try using MT8870,88.

4) Dont forget to place an RC filter at the I/P and O/p stage.


5) place a logic analyser at the data pins of your uc and see your
self what exactly is happening please dont say you dont have one:)

6) I feel here the problem is with the distorted signal at the input stage
Check your program also are you handling the TOE pin correctly?.

Do this course first and lets see what are the results ?


rgds
sanjeev

PS:Make onething very sure either your S/W or H/W otherwise you'll
Keep toppling :)).


========================================Txip you idea is infact good Buy, Break, Make and sell :) Simon will
take some more time to understand this technique Haaa.
========================================