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⌂ ∞ ▽ Elite on the 6502

Drawing the screen: CLYNS

[6502 Second Processor version]

       Name: CLYNS                                                   [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Clear the bottom three text rows of the mode 1 screen by sending a
             #clyns command to the I/O processor

    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:
             * dockEd calls CLYNS
             * EQSHP calls CLYNS
             * hm calls CLYNS
             * JMTB calls CLYNS
             * qv calls CLYNS
             * TITLE calls CLYNS
             * TT219 calls CLYNS
             * SCAN calls via SC5




 Returns:

   A                    A is set to 0

   Y                    Y is set to 0



 Other entry points:

   SC5                  Contains an RTS



.CLYNS

 LDA #%11111111         \ Set DTW2 = %11111111 to denote that we are not
 STA DTW2               \ currently printing a word

 LDA #%10000000         \ Set bit 7 of QQ17 to switch standard tokens to
 STA QQ17               \ Sentence Case

 LDA #21                \ Move the text cursor to column 1, row 21
 STA YC
 LDA #1
 STA XC

 LDA #clyns             \ Send a #clyns command to the I/O processor to clear
 JSR OSWRCH             \ the bottom three text rows of the top part of the
 JSR OSWRCH             \ screen

 LDA #0                 \ Set A = 0

 TAY                    \ Set Y = 0

.SC5

 RTS                    \ Return from the subroutine