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Used by the routines at COPY_LINE and STMT_RET.
This subroutine is called in several instances to read the BREAK key. The carry flag is returned reset only if the SHIFT and the BREAK keys are both being pressed.
BREAK_KEY 08020 LD A,127 Form the port address 32766 and read in a byte.
08022 IN A,(254)
08024 RRA Examine only bit 0 by shifting it into the carry position.
08025 RET C Return if the BREAK key is not being pressed.
08026 LD A,254 Form the port address 65278 and read in a byte.
08028 IN A,(254)
08030 RRA Again examine bit 0.
08031 RET Return with carry reset if both keys are being pressed.
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