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Routines |
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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.
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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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