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Routines |
| Prev: 63005 | Up: Map | Next: 63134 |
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| 63040 | PUSH HL | Store HL | ||||||
| 63041 | LD DE,28248 | Point DE at 28248 | ||||||
| 63044 | ADD A,A | Double A... | ||||||
| 63045 | LD H,0 | ...load into HL... | ||||||
| 63047 | LD L,A | ... | ||||||
| 63048 | ADD HL,HL | ...double again... | ||||||
| 63049 | ADD HL,HL | ...and again to get 8 times original A value... | ||||||
| 63050 | ADD HL,DE | ...and add DE to this | ||||||
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At this point, HL points to one of the five sets of axe frame graphic data (28504, 29176, 29184, 29192 or 29200).
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| 63051 | PUSH HL | Copy HL into IX... | ||||||
| 63052 | POP IX | ... | ||||||
| 63054 | LD BC,(23677) | Load value in coordinate storage into BC (holds x- and y-coordinates of axe) | ||||||
| 63058 | CALL 63134 | Load HL with display file address for coordinates in BC | ||||||
| 63061 | LD C,A | Load pixel-within-byte "address" into C | ||||||
| 63062 | LD B,8 | Load 8 into B (as axe graphic data comprises 8 pixel rows) | ||||||
| 63064 | LD D,(IX+0) | Load a byte of axe graphic data into D | ||||||
| 63067 | LD A,C | Load pixel-within-byte "address" into A | ||||||
| 63068 | OR A | Check if we're dealing with pixel zero... | ||||||
| 63069 | JR Z,63128 | ...and if so, skip ahead to 63128 | ||||||
| 63071 | XOR A | Set A to zero | ||||||
| 63072 | LD E,A | Copy into E | ||||||
| 63073 | PUSH BC | Store BC (B=graphic row counter, C=pixel-within-byte "address") | ||||||
| 63074 | LD B,C | Copy pixel-within-byte "address" into B | ||||||
| 63075 | SRL D | Shift graphic data right one bit (rightmost bit goes into carry flag) | ||||||
| 63077 | RRA | Rotate carry flag into leftmost bit of A, shifting other bits right | ||||||
| 63078 | SCF | Set carry flag | ||||||
| 63079 | RR E | Rotate (set) carry flag into leftmost bit of E, shifting other bits right, and resetting carry flag | ||||||
| 63081 | DJNZ 63075 | Repeat loop to shift graphic right another pixel if necessary | ||||||
| 63083 | EX AF,AF' | Switch AF registers | ||||||
| 63084 | LD A,E | Load A with value in E (set bits represent number of pixels by which axe graphic has been shifted right) | ||||||
| 63085 | POP BC | Restore BC (B=graphic row counter, C=pixel-within-byte "address") | ||||||
| 63086 | LD A,D | Load left part of axe graphic data into A | ||||||
| 63087 | LD E,(HL) | Load E with graphic data currently at axe's position on screen | ||||||
| 63088 | XOR E | Blend axe graphic data with what is already on screen at its position to make things look more natural... | ||||||
| 63089 | LD (HL),A | ...and write new graphic data back to screen | ||||||
| 63090 | INC HL | Advance right one byte in display file | ||||||
| 63091 | EX AF,AF' | Switch registers to restore right part of axe graphic data to A | ||||||
| 63092 | LD E,(HL) | Load E with graphic data currently at axe's position on screen | ||||||
| 63093 | XOR E | Blend axe graphic data with what is already on screen at its position to make things look more natural... | ||||||
| 63094 | LD (HL),A | ...and write new graphic data back to screen | ||||||
| 63095 | DEC HL | Move left one byte in display file | ||||||
| 63096 | INC IX | Advance IX to next row of axe graphic data | ||||||
| 63098 | INC H | Increase H by 1 (i.e. advance HL by 256) | ||||||
| 63099 | LD A,H | If at least one of the three rightmost bits of H are set (i.e. we haven't crossed over from one third of the display to the next third) then skip ahead to 63124 (as HL now points to next pixel row down) | ||||||
| 63100 | AND 7 | |||||||
| 63102 | JR NZ,63124 | |||||||
| 63104 | LD A,H | Else we must have been in the bottom pixel row of a character row, so decrease H by 8 (1 to go back up, then 7 pixel rows up to the top of that character row) | ||||||
| 63105 | SUB 8 | |||||||
| 63107 | LD H,A | |||||||
| 63108 | LD A,L | Advance L by 32 bytes to move down one character row, so now the top of the next character row down... | ||||||
| 63109 | ADD A,32 | ... | ||||||
| 63111 | LD L,A | ... | ||||||
| 63112 | JR NC,63124 | If L hasn't gone over 256 (i.e. we haven't moved 32 bytes on from the top pixel row of the bottom character row of the third) then skip ahead to 63124 else move down by a third | ||||||
| 63114 | LD A,H | |||||||
| 63115 | ADD A,8 | |||||||
| 63117 | LD H,A | |||||||
| 63118 | XOR 88 | If we have not reached the start of the attribute file... | ||||||
| 63120 | JR NZ,63124 | ...then skip ahead to 63124 | ||||||
| 63122 | LD H,64 | ...else wrap back round to the start of display file again | ||||||
| 63124 | DJNZ 63064 | Decrease B (remaining number of pixel rows to draw) and loop back to 63064 | ||||||
| 63126 | POP HL | Restore HL | ||||||
| 63127 | RET | Return | ||||||
| 63128 | XOR A | Set A to zero | ||||||
| 63129 | EX AF,AF' | Switch registers | ||||||
| 63130 | XOR A | Set A to zero | ||||||
| 63131 | LD E,A | Set E to zero as axe graphic hasn't been shifted | ||||||
| 63132 | JR 63086 | Jump back to 63086 | ||||||
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