So I stop screwing this up over and over,
Method for determinging A GT B for two unsigned integers using standard subtractor in VHDL:
where f(x,y) = x-y = x + 2's complement(y),
carry out of f(B-A) shows B > A. not f(A-B).
Examples:
1) is 70128 GT 65535?
for 24 bit case,
B = 70128 = x0111F0
A = 65535 = x00FFFF, 2s_comp(B) = xFF0001
B - A = x0111F0 + xFF0001 = x10011F1, carry out is 1, remainder = B-A = 4593
2) is 32768 GT 65535?
for 24 bit case,
B = 32768 = x008000
A = 65535 = x00FFFF, 2s_comp(B) = xFF0001
B - A = x008000 + xFF0001 = xFF8001, carry out is 0, remainder = B-A = -32767
