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Routines |
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This section of code is entered at various points. The main entry point below is used by the startup routine at 5EE0.
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| 6900 | LD SP,$5CFE | Put the stack pointer somewhere safe | ||
| 6903 | CALL $7E86 | Play the theme tune | ||
| 6906 | JR $6916 | Enter demo mode | ||
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This entry point is used by the routine at F9F6 when ERIC has been sent home (either for having mumps or for having over 10000 lines).
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| 6908 | CALL $7ED6 | Remove the speech bubble | ||
| 690B | LD DE,($7FC4) | DE=score | ||
| 690F | AND A | Reset the carry flag ready for a subtraction | ||
| 6910 | SBC HL,DE | Subtract the score from the high score... | ||
| 6912 | ADD HL,DE | ...and add it back again | ||
| 6913 | JR NC,$6916 | Jump unless we have a new high score | ||
| 6915 | EX DE,HL | HL=new high score | ||
| 6916 | LD A,$FF | 0xFF: demo mode | ||
| 6918 | JR $6921 | |||
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This entry point is used by the routine at 7DFA when exiting demo mode.
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| 691A | CALL $EDE0 | Ask for the input method, and change the character names (if desired) | ||
| 691D | LD HL,($7FC2) | HL=high score | ||
| 6920 | XOR A | 0x00: game mode (as opposed to demo mode) | ||
| 6921 | LD SP,$5CFE | Put the stack pointer somewhere safe | ||
| 6924 | PUSH HL | Save the high score | ||
| 6925 | LD E,A | E=0xFF (demo mode) or 0x00 | ||
| 6926 | LD A,($7FF9) | Collect the current lesson number (0x00-0x3F) from 7FF9 | ||
| 6929 | AND $30 | Set A to 0x0F, 0x1F, 0x2F or 0x3F (lessons 0x00, 0x10, 0x20, and 0x30 are PLAYTIME) | ||
| 692B | ADD A,$0F | |||
| 692D | LD D,A | D=new lesson number minus one | ||
| 692E | PUSH DE | Save this for now | ||
| 692F | CALL $F70A | Unflash the safe and all shields | ||
| 6932 | LD HL,$7FFD | 7FFD holds the number (0x98-0xAB) of the last character moved | ||
| 6935 | LD (HL),$97 | Reset this number so 0x98 (little boy no. 1) is moved next | ||
| 6937 | DEC L | Blank out the rest of the game status buffer (except for the random number seed at 7FFE) | ||
| 6938 | LD (HL),$00 | |||
| 693A | JR NZ,$6937 | |||
| 693C | LD L,$E8 | Initialise ERIC's main action timer at 7FE8 | ||
| 693E | LD (HL),$11 | |||
| 6940 | LD L,$F9 | HL=7FF9 (which holds the lesson number, 0x00-0x3F) | ||
| 6942 | POP DE | Restore the lesson number to D and game mode indicator (0x00 or 0xFF) to E | ||
| 6943 | LD (HL),D | Set the lesson number | ||
| 6944 | LD L,$F7 | Set the lesson clock (at 7FF7) to 1 | ||
| 6946 | INC (HL) | |||
| 6947 | INC E | If a new game is starting, prepare the shields and safe, and play the theme tune | ||
| 6948 | CALL NZ,$F8B4 | |||
| 694B | POP HL | Restore the high score to HL, and save it in 7FC2 | ||
| 694C | LD ($7FC2),HL | |||
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The following loop sets the initial animatory state, location and character flags (byte 0x7A of the buffer) for each character (including ERIC).
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| 694F | LD H,$98 | 0x98=little boy no. 1 | ||
| 6951 | LD DE,$DB00 | The data table at DB00 holds the initial animatory states of the characters | ||
| 6954 | LD L,$60 | Point HL at byte 0x60 of the character buffer | ||
| 6956 | LD A,(DE) | Set the initial animatory state of the character | ||
| 6957 | LD (HL),A | |||
| 6958 | INC L | L=0x61 | ||
| 6959 | INC D | The data table at DC00 holds the initial x-coordinates of the characters | ||
| 695A | LD (HL),$A9 | All characters start on the bottom floor (y=169) | ||
| 695C | INC L | L=0x62 | ||
| 695D | LD A,(DE) | Pick up the character's initial x-coordinate | ||
| 695E | INC D | The data table at DD00 holds the character flags | ||
| 695F | LD (HL),A | Set the character's initial x-coordinate | ||
| 6960 | LD A,(DE) | Pick up the character flags (0x00=kid; 0x10=adult; 0x20=pellet) | ||
| 6961 | DEC D | Point DE back at the table of initial animatory states | ||
| 6962 | DEC D | |||
| 6963 | INC E | Next character | ||
| 6964 | LD B,$1D | Blank out the remaining 29 bytes of the character's buffer | ||
| 6966 | INC L | |||
| 6967 | LD (HL),$00 | |||
| 6969 | DJNZ $6966 | |||
| 696B | LD L,$7A | Place the character flags into byte 0x7A of the character's buffer | ||
| 696D | LD (HL),A | |||
| 696E | INC L | |||
| 696F | INC L | L=0x7C | ||
| 6970 | LD (HL),$9F | Place the address of the continual subcommand routine at 629F (RET) into bytes 0x7C and 0x7D of the character's buffer | ||
| 6972 | INC L | |||
| 6973 | LD (HL),$62 | |||
| 6975 | INC H | Next character | ||
| 6976 | INC A | Have we done all the non-player characters? | ||
| 6977 | JR NZ,$6954 | Jump back to do the next one if not | ||
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All that remains now is to print the logo, lesson box and score box, and bring the skool into view.
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| 6979 | CALL $6B0E | Print the bottom 3 lines of the screen | ||
| 697C | JP $F918 | Scroll the skool into view and enter the main loop | ||
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