Having a problem computing an LRC checksum.
This compiles OK, but the Checksum I end up with is FF no matter what. Am I just using this "^=" operator wrong?

Checksum = 0xFF; //-Initialize checksum
while (!TI0);
TI0 = 0;
SBUF0 =0x01;//SOF
while (!TI0);
TI0 = 0;
SBUF0 = Len; // Length of frame incl. Len excl. Chcksm
Checksum ^= Len;
while (!TI0);
TI0 = 0;
SBUF0 = Type;
Checksum ^= Type;
while (!TI0);
TI0 = 0;
SBUF0 = Cmd;
Checksum ^= Cmd;
while (!TI0);
TI0 = 0;
SBUF0 = Node;
Checksum ^= Checksum;
while (!TI0);
TI0 = 0;
SBUF0 = CommLen; //data payload length (button,pressed state)
Checksum ^= CommLen;
while (!TI0);
TI0 = 0;
SBUF0 = CommClass; // COMMAND_CLASS_BASIC
Checksum ^= CommClass;
while (!TI0);
TI0 = 0;
SBUF0 = Comm;//Basic_Set
Checksum ^= Comm;
while (!TI0);
TI0 = 0;
SBUF0 = (LastKey);
Checksum ^= LastKey;
while (!TI0);
TI0 = 0;
SBUF0 = TXOpt; //tx option ACK needed
Checksum ^= TXOpt;
while (!TI0);
TI0 = 0;
SBUF0 = FuncID; //dummy funcID
Checksum ^= FuncID;
while (!TI0);
TI0 = 0;
SBUF0 = Checksum;

Using Keil Compiler, running on a Silabs C8051F330 if that matters.
Thanks