How can I find text mode page buffer in TASM?

I'm trying to send some characters to page 1 of text mode by its memory address, but I find no suitable result, I calculated the page 1 address like this "0B800h + 1000h = 0C800h".

This is my code:

        IDEAL

        MODEL   small
        STACK   256

        DATASEG


exCode          DB      0
x_var           db      219


        CODESEG


Start:  
        mov     ax, @data       ; Initialize DS to address
        mov     ds, ax          ;  of data segment
        

        ; Page 1
        mov     ax, 0501h
        int     10h

        ;Page 1 buffer -> es
        mov     ax, 0C800h
        mov     es, ax
        
        mov     si, offset x_var

        mov     di, (10*80*2)+(10*2)

        cld

        lodsb
        stosb

        ; wait for any key press: 
        mov ah, 0
        int 16h

        ;Page 0 again
        mov     ax, 0500h
        int     10h


Exit:
        mov     ah, 04Ch        ; DOS function: Exit program
        mov     al, [exCode]    ; Return exit code value
        int     21h             ; Call DOS.  Terminate program

        END     Start           ; End of program / entry point