WriteControl    Macro
    local wait
    
    push ax
    mov dx,3B1h

wait:
    in al,dx
    and al,3
    cmp al,3
    jne wait    
;
    pop ax
    out dx,al
                Endm

                
WriteData    Macro
    local wait

    push ax
    mov dx,3B1h

wait:
    in al,dx
    and al,3
    cmp al,3
    jne wait
;
    pop ax        
    dec dx
    out dx,al
                Endm
                


TestDisp:
    mov al,81h      ; CGROM mode, OR mode
    WriteControl
;
    xor al,al
    WriteData
    xor al,al
    WriteData
    mov al,42h
    WriteControl    ; set graphics home = 0000
;
    mov al,28h
    WriteData
    xor al,al
    WriteData
    mov al,43h
    WriteControl    ; set graphics area = 0028
;
    xor al,al
    WriteData
    mov al,20h
    WriteData
    mov al,40h
    WriteControl    ; set text home = 2000
;
    mov al,28h
    WriteData
    xor al,al
    WriteData
    mov al,41h
    WriteControl    ; set text area = 0028
;
    mov al,3
    WriteData
    xor al,al
    WriteData
    mov al,22h
    WriteControl    ; set CGRAM offset = 03
;
    mov al,9Ah
    WriteControl    ; graphics on, text on, cursor off
;
    xor al,al
    WriteData
    xor al,al
    WriteData
    mov al,24h
    WriteControl
;
    mov al,0B0h
    WriteControl
;
    xor si,si

ylo:
    xor di,di

ilo:
    cmp di,1
    je ilo_ff
;
    cmp di,28
    je ilo_ff
;
    cmp si,1
    jle ilo_norm
;
    cmp si,8
    jg ilo_norm

ilo_ff:
    mov al,0FFh
    WriteData
    jmp ilo_next

ilo_norm:
    cmp di,15
    jne ilo_00
    cmp si, 8 * 8
    jge ilo_00
;
    mov al,55h
    WriteData
    jmp ilo_next

ilo_00:
    xor al,al
    WriteData

ilo_next:
    inc di    
    cmp di,40
    jb ilo

ylo_next:
    inc si
    cmp si,16 * 8
    jb ylo
;
    mov al,0B2h
    WriteControl