The DOVDU19 subroutine - Elite on the BBC Micro and NES

       Name: DOVDU19                                                 [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Change the mode 1 palette
    Context: See this subroutine in context in the source code
 Variations: See code variations for this subroutine in the different versions
 References: This subroutine is called as follows:
             * HALL calls DOVDU19
             * LOOK1 calls DOVDU19
             * TITLE calls DOVDU19
             * TRADEMODE calls DOVDU19
             * TT22 calls DOVDU19
             * TT23 calls DOVDU19


 This routine updates the VNT3+1 location in the IRQ1 handler to change the
 palette that's applied to the top part of the screen (the four-colour mode 1
 part). The parameter is the offset within the TVT3 palette block of the
 desired palette.


 Arguments:

   A                    The offset within the TVT3 table of palettes:

                          * 0 = Yellow, red, cyan palette (space view)

                          * 16 = Yellow, red, white palette (charts)

                          * 32 = Yellow, white, cyan palette (title screen)

                          * 48 = Yellow, magenta, white palette (trading)


.DOVDU19

 STA VNT3+1             \ Store the new colour in VNT3+1, in the IRQ1 routine,
                        \ which modifies which TVT3 palette block gets applied
                        \ to the mode 1 part of the screen

 RTS                    \ Return from the subroutine
Drawing the screen: DOVDU19

[BBC Master version]
