Problem with MOV, syntax in Xtensa assembler

[MPETREMANN11]

Hello,

I'm testing XTENSA assembler.

And I've a problem with MOV,

My test:

    a8 a2       MOV,

ESP32forth display:

-->     a8 a2       MOV,
STACK UNDERFLOW ERROR

I use only ar as registers before MOV, because in ISA XTENSA, I read this:

In this documentation, MOV need only two registers.....

With best regards