Exception on arithmetic operation

[eeboy]

Why does this bit of code throw an exception?

dim dataBytes(5) as byte

dataBytes(0)=&H4A
dataBytes(1)=&H1
dataBytes(2)=&H1
dataBytes(3)=&H2A
dataBytes(4)=(dataBytes(1)+dataBytes(2)+dataBytes(3))^&HFF

The final statement is what generates the exception. The exception states that an arithmetic operation resulted in an overflow.

Thanks!