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Routines |
| Prev: 8039 | Up: Map | Next: 80C1 |
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Used by the routine at 80FD.
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Checks if the player has picked a control option on menu 1 (8039).
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| 80A1 | LD BC,$F7FE | Port input address for keyboard keys 1,2,3,4 and 5 | ||
| 80A4 | IN A,(C) | Get input from port | ||
| 80A6 | OR %11100000 | To maintain keyboard consistency, set bits 5-7 ready for the CP in the next instruction | ||
| 80A8 | CP %11111111 | Are any keys currently being pressed? | ||
| 80AA | JR Z,$80B8 | If not (value = 255), check if a key press has previously been registered | ||
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Key is being pressed - check if it's a valid option (1,2,3 or 4), and if so, jump to 80C1.
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| 80AC | LD B,$04 | 4 port addresses to check | ||
| 80AE | LD HL,$8BB2 | Address pointer to where the port addresses are held | ||
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Loop through port addresses
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| 80B1 | CP (HL) | Compare with keyboard input | ||
| 80B2 | JR Z,$80C1 | If a valid key has been pressed, jump to 80C1 to play a sound and highlight the choice on screen | ||
| 80B4 | INC HL | Otherwise advance to the next (2 byte) port address | ||
| 80B5 | INC HL | |||
| 80B6 | DJNZ $80B1 | ...and keep checking until all 4 are done. | ||
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Check if a key press has been registered already
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| 80B8 | LD A,($8BAA) | Has a menu option (1-4) been chosen yet? | ||
| 80BB | CP $00 | |||
| 80BD | JR Z,$80A1 | If not, go back to checking keys at 80A1 | ||
| 80BF | JR $80FD | If so, run the routine to see if ENTER is being pressed (to start the game) | ||
| Prev: 8039 | Up: Map | Next: 80C1 |