AMPMFlag=AMPMFlag^1 '>>>>>>>>>>>>>>>>>>>what does this do?

AMPMFlag is a BIT variable.
All this does is toggle the BIT variable, if it was zero it will be set to 1, if it was 1 it will be set to 0. It is the equivallent of...

IF AMPMFlag=0 then
AMPMFlag=1
else
AMPMFlag=0
endif



Lc var byte [15]
For i = 0 to 15 : read i, b0:if b0 = 0 then
lookup i,[1,2,3,11,4,5,6,11,7,8,9,10,11,12,13,14], b0
Lc(i)=b0 '>>>>>>>>>>>>>>>>>>>>>>>>>>>what does this do?

Lc is a BYTE array 15 elements deep in the range Lc(0) to Lc(14)
You are loading Lc at array location i with the contents of variable b0