8086 trainer problem

Hi!
I wrote for a simple program for complementing the content of address 0300:0 and save it in address 0300:1.

Here is my program

OUTPUT 2500AD
ORG 2000H
MOV DX,0FFE6H
MOV AX,82H
OUT DX,AL
NEXT:MOV AX,3000H
MOV BX,0000H
CALL DISP
NOT AL
MOV 3001H,AL
MOV BX,0100H
CALL DISP
JMP SHORT NEXT
DISP:PUSH AX
MOV CX,1
CALL FAR 0FF00:0B12H
POP AX
RET
END
I am using 8086 trainer kit to test it.But this program takes the 3000H as the data and shows on the data display.The result that complemented is 30FFH on address display.Can someone tell me what goes wrong in my program?
I initially load 20H as the 1 byte data in address 3000H.
Thanks!