41CL CLXPMEM - YSTO, YRCL and YX<> index problem

[Podalirius]

Hi, I am studying the CLXPMEM module.
In a test on my nsimII emulator (soon I will receive my 41CL board)
with the command YSTO, value 500, I think that the vale of the X register
is stored in the register number 500, But with YRCL 500 I do not obtain any value.
With YSTO 500 and YRCL 500 no errors is displayed.
But if I use the command YX<> 500 the value of X register is swapped with
the register number 500, as I can expect to obtain.
I chose the value 500 because is in the range of MAIN memory addresses
(192-511, Hex 0CD-1FF). Where I am wrong?
Thank you so much for every help!!!