82h DP$MSET set display mode
Input A register - mode required: 0 for 2-line, 1 for 4-line mode.
Bit 7 set specifies leave clock alone.
Output A register - previous mode.
Description Sets the Operating System into 2 or 4 line mode.

The following is always carried out:

  1. If the top bit of the A register is clear, the UDG CLOCK is switched off.
  2. The variable DPB_MCHK is cleared.
  3. END if the mode requested is the same as the current mode.
  4. The screen is initilised for the mode selected:
    2-line: clear 16 character by 2 line window with border.
    4-line: clear entire 4-line screen.
  5. The variables DPA_SCRN, DPB_NLIN, DPB_WIDE are initialised.

The B and X registers are preserved.

This call is not available on CM/XP machines.

Example Machine-code applications for 2 and 4 line machines can use the following code:
        LDAA    DPB_MODE
        BEQ     TWO              ;branch to run in 2-line mode
        OS      DP$MSET          ;set to 4-line mode A=1

        ;PUT 4-LINE CODE HERE

        RTS

TWO:    ;PUT 2-LINE CODE HERE

        RTS
Errors - none -