QDOS Internals

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====== SD_SETMD/IOW_SOVA ======

This trap sets the character writing or plotting mode.

^Call Parameters^^Return Parameters^^
|D0.B|$2C|D0.L|Error code.|
|D1.W|Mode |D1.L|Corrupted.|
|D3.W|Timeout. |D3.L|Preserved.|
|A0.L|Channel ID. |A0.L|Preserved.|
|A1.L| |A1.L|Corrupted.|

===== Errors =====


|ERR_NC|Not complete.|
|ERR_NO|Channel not open.|


===== Notes =====
  * All registers not shown above are not used on entry and are preserved on exit.
  * The mode given in D1 is:
    * -1 ink XORed into the background.
    * 0 character background is strip colour; plotting is in ink colour.
    * 1 character background is transparent so it is not overwritten; plotting is in ink colour.

===== Example =====
The example below shows how to use this trap call to make printing appear and then disappear. The mode is set to -1 then printing can be done. After a wait the printing is again done and it now disappears. It is assumed that A0 contains the channel ID.

<code>
Setmd   moveq   #-1,d1          ; Set XOR mode.
        moveq   #-1,d3          ; Timeout.
        moveq   #SD_SETMD,d0    ; $2C
        trap    #3              ; Set the mode
        tst.l   d0              ; OK? . .
        bne     error ---->     ; . . no!
        bsr     print           ; Print something at 0,0
        bsr     wait            ; Wait for a bit.
        bsr     print           ; The printing disappears.
</code>

QDOS Internals

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