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Routines |
D | skool y-coordinate (152-172) |
E | skool x-coordinate (0-95) |
24843 | LD A,E | A=skool x-coordinate (0-95) |
24844 | AND 96 | Now H is one of: 128 if 0<=E<32 136 if 32<=E<64 144 if 64<=E<96 |
24846 | RRCA | |
24847 | INC A | |
24848 | RRCA | |
24849 | LD H,A | |
24850 | LD A,(DE) | A=skool UDG reference for the character square at (E,D) |
24851 | PUSH DE | |
24852 | LD L,A | HL=base address of the UDG bytes for the character square at (E,D) |
24853 | LD BC,2048 | B=8, C=0 |
24856 | LD DE,32513 | Copy the 8 bytes of the skool UDG into the back buffer at 32513-32520 |
24859 | LD A,(HL) | |
24860 | LD (DE),A | |
24861 | INC H | |
24862 | INC E | |
24863 | DJNZ 24859 | |
24865 | NOP | |
24866 | POP DE | Restore the skool coordinates to DE |
24867 | LD B,21 | There are 21 characters to consider |
24869 | LD H,152 | 152=little boy no. 1 |
24871 | LD L,98 | Byte 98 of the character's buffer holds his x-coordinate |
24873 | LD A,E | A=skool x-coordinate (0-95) |
24874 | SUB (HL) | Subtract the character's x-coordinate |
24875 | DEC HL | Byte 97 of the character's buffer holds his y-coordinate |
24876 | JR C,24926 | Jump if no part of the character's sprite appears at this x-coordinate |
24878 | CP 3 | |
24880 | JR NC,24926 | |
24882 | ADD A,A | Now C is 0, 4 or 8, corresponding to the column (left, middle or right) of the character's sprite that aligns with x-coordinate E |
24883 | ADD A,A | |
24884 | LD C,A | |
24885 | LD A,D | A=skool y-coordinate (152-172) |
24886 | SUB (HL) | Subtract the character's y-coordinate |
24887 | JR C,24926 | Jump if no part of the character's sprite appears at this y-coordinate |
24889 | CP 4 | |
24891 | JR NC,24926 | |
24893 | ADD A,C | A=0-11, corresponding to the sprite tile that appears at (E,D) |
24894 | EXX | |
24895 | ADD A,173 | |
24897 | LD H,A | H'=173-184 |
24898 | EXX | |
24899 | LD L,96 | Pick up the character's animatory state in A |
24901 | LD A,(HL) | |
24902 | EXX | |
24903 | LD L,A | L'=character's animatory state |
24904 | LD A,(HL) | A=sprite tile UDG reference |
24905 | AND A | Is it the blank UDG? |
24906 | JR Z,24925 | Jump if so |
24908 | CALL 27914 | Get the base address of the sprite tile UDG bytes in HL' |
24911 | LD B,8 | There are 8 bytes in the UDG |
24913 | LD DE,32513 | |
24916 | LD A,(DE) | A=back buffer UDG byte |
24917 | OR (HL) | OR in the sprite tile UDG byte |
24918 | INC H | |
24919 | AND (HL) | AND in the sprite tile UDG mask |
24920 | INC H | |
24921 | LD (DE),A | |
24922 | INC E | |
24923 | DJNZ 24916 | Jump back until the UDG is done |
24925 | EXX | |
24926 | INC H | Next character |
24927 | DJNZ 24871 | Jump back to consider the next character |
24929 | LD HL,32512 | 32512 holds the leftmost column of the skool on-screen (0-64) |
24932 | LD A,D | A=skool y-coordinate (152-172) |
24933 | AND 7 | Set C to the LSB of the display file address corresponding to the screen coordinates (0,D-152) |
24935 | RRCA | |
24936 | RRCA | |
24937 | RRCA | |
24938 | LD C,A | |
24939 | LD A,E | A=screen x-coordinate (0-31) |
24940 | SUB (HL) | |
24941 | ADD A,C | Set L to the LSB of the display file address corresponding to the skool coordinates (E,D) |
24942 | LD L,A | |
24943 | LD A,D | A=screen y-coordinate (0-20) |
24944 | SUB 152 | |
24946 | AND 24 | Set H to the MSB of the display file address corresponding to the skool coordinates (E,D) |
24948 | ADD A,64 | |
24950 | LD H,A |
24951 | LD B,8 | Copy the tile to the screen |
24953 | LD DE,32513 | |
24956 | LD A,(DE) | |
24957 | LD (HL),A | |
24958 | INC H | |
24959 | INC E | |
24960 | DJNZ 24956 | |
24962 | RET |