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I built a digital oscilloscope but i have a problem in the trigger mechanism...

The write side is alredy ok, but in the read side i cant make the trigger be in the mid of the window...

reg [8:0] rdaddress, SendCount;
reg Sending;
wire TxD_busy;

always @(posedge clk)
if(~Sending)
begin
Sending <= AcquisitionStarted;
if(AcquisitionStarted) rdaddress <= (wraddress_triggerpoint ^ 9'h100);
end
else
if(~TxD_busy)
begin
rdaddress <= rdaddress + 1;
SendCount <= SendCount + 1;
if(&SendCount) Sending <= 0;
end

i think the problem is here:
rdaddress <= (wraddress_triggerpoint ^ 9'h100);

What that mean?
Is that realy a bitwise xor?

Thanks for any help!