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Elite on the BBC Micro

Utility routines: clr_scrn [Elite-A, I/O processor]

Name: clr_scrn [Show more] Type: Subroutine Category: Utility routines Summary: Clear the top part of the screen (the space view)
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * tube_table calls clr_scrn

This routine is run when the parasite sends a clr_scrn command. It clears the top part of the screen (the mode 4 space view).
.clr_scrn LDX #&60 \ Set X to the screen memory page for the top row of the \ screen (as screen memory starts at &6000) .BOL1 JSR ZES1 \ Call ZES1 to zero-fill the page in X, which clears \ that character row on the screen INX \ Increment X to point to the next page, i.e. the next \ character row CPX #&78 \ Loop back to BOL1 until we have cleared page &7700, BNE BOL1 \ the last character row in the space view part of the \ screen (the top part) RTS \ Return from the subroutine