Routines
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DE69: Draw Tile
Used by the routine at F801.
Draw_Tile DE69 LD IX,$DF58 Set IX to Table_TileDataOffsets.
DE6D LD B,$00 Initialise B to 00 for the sum below.
DE6F LD A,($E2C7) Load *Item_ID into A.
Find which spritesheet the image is located in. There are 14 sprites in each sheet, so test if the sprite ID is less than 15 to check if it's in the first one. Else, subtract 14 and check again.
DE72 LD C,$03 Set a counter in C with 03 to track the three spritesheets (two item sheets and one for the game tiles).
FindSpritesheet_Loop DE74 CP $15 Jump to LocateSprite if A is lower than 15 (unsigned comparison).
DE76 JP M,LocateSprite
DE79 SUB $14 Subtract 14 from A.
DE7B DEC C Decrease C by one.
DE7C JR NZ,FindSpritesheet_Loop Jump back to FindSpritesheet_Loop until C is zero.
Default the sprite ID to 01.
DE7E LD A,$01 A=01.
Adjust the sprite ID for 0-based indexing.
LocateSprite DE80 DEC A Decrease the sprite ID by one.
There are 04 offset bytes, so multiply the sprite ID by 04 to find the relevant offsets in the table.
DE81 RLCA Multiply the sprite ID by 04 and store the result in C.
DE82 RLCA
DE83 LD C,A
Fetch the offsets for the sprite being processed.
DE84 ADD IX,BC Add the result to IX to locate the offsets for the tile.
DE86 LD C,(IX+$00) Fetch the graphic data offset and store it in BC.
DE89 LD B,(IX+$01)
DE8C LD E,(IX+$02) Fetch the attribute data offset and store it in DE.
DE8F LD D,(IX+$03)
Calculate the graphic data address.
DE92 LD IX,($E2C8) Add *Item_SpriteBank and the offset in BC to locate the start of the graphics data - store the result in IX.
DE96 ADD IX,BC
Calculate the attribute address.
DE98 LD HL,($E2C8) Add *Item_SpriteBank and 0A00 to locate the start of the attributes for the spritesheet. Then, add the offset held in DE to the total, this will locate the start of the attributes for the sprite currently being processed - store the result in IY (using the stack).
DE9B LD BC,$0A00
DE9E ADD HL,BC
DE9F ADD HL,DE
DEA0 PUSH HL
DEA1 POP IY
Print the sprite to the screen.
DEA3 LD B,$04 B=04.
DEA5 LD H,$28 H=28.
Draw_Tile_0 DEA7 PUSH BC Stash BC on the stack.
DEA8 LD A,$08 A=08.
DEAA PUSH IX Stash IX on the stack.
DEAC LD BC,$0014 BC=0014.
Draw_Tile_1 DEAF PUSH AF Stash AF on the stack.
DEB0 LD L,A L=A.
DEB1 CALL CalculateScreenAddress Call CalculateScreenAddress.
DEB4 LD A,(IX+$00) Write *IX+00 to *DE.
DEB7 LD (DE),A
DEB8 ADD IX,BC IX+=BC.
DEBA POP AF Restore AF from the stack.
DEBB INC A Increment A by one.
DEBC CP $28 Jump to Draw_Tile_1 if A is not equal to 28.
DEBE JP NZ,Draw_Tile_1
Switch IX to point to the attributes.
DEC1 PUSH IY IX=IY (using the stack).
DEC3 POP IX
DEC5 LD DE,$5825 DE=5825 (attribute buffer location).
DEC8 LD B,$04 B=04.
DECA PUSH HL Stash HL on the stack.
Colour_Tile_Loop DECB PUSH BC Stash BC on the stack.
DECC LD A,(IX+$00) Write *IX+00 to *DE.
DECF LD (DE),A
DED0 LD BC,$0014 IX+=0014.
DED3 ADD IX,BC
DED5 LD HL,$0020 DE+=0020.
DED8 ADD HL,DE
DED9 EX DE,HL
DEDA POP BC Restore BC from the stack.
DEDB DJNZ Colour_Tile_Loop Decrease counter by one and loop back to Colour_Tile_Loop until counter is zero.
DEDD POP HL Restore HL, IX and BC from the stack.
DEDE POP IX
DEE0 POP BC
DEE1 LD A,B A=B.
DEE2 PUSH BC Stash BC, IX and HL on the stack.
DEE3 PUSH IX
DEE5 PUSH HL
DEE6 CP $01 Jump to Draw_Tile_7 if A is equal to 01.
DEE8 JP Z,Draw_Tile_7
DEEB LD A,$05 A=05.
DEED LD C,$23 C=23.
Draw_Tile_2 DEEF LD B,C B=C.
DEF0 SLA B Shift B left (with carry).
Draw_Tile_3 DEF2 DJNZ Draw_Tile_3 Decrease counter by one and loop back to Draw_Tile_3 until counter is zero.
DEF4 XOR %00010000 Flip bit 4.
DEF6 OUT ($FE),A Send to the speaker.
DEF8 DEC C Decrease C by one.
DEF9 JP NZ,Draw_Tile_2 Jump to Draw_Tile_2 until C is zero.
DEFC LD HL,$1388 HL=1388.
DEFF LD DE,$04E2 DE=04E2.
Draw_Tile_4 DF02 LD A,(HL) A=*HL.
DF03 AND %11110000 Keep only bits 4-7.
DF05 OR %00000101 Set bits 0, 2.
DF07 OUT ($FE),A Send to the speaker.
DF09 INC HL Increment HL by one.
DF0A DEC DE Decrease DE by one.
DF0B LD A,D Jump to Draw_Tile_4 if DE is not zero.
DF0C OR E
DF0D JP NZ,Draw_Tile_4
DF10 LD A,$01 Write 01 to *Tile_Horizontal_Coordinate.
DF12 LD ($E75F),A
DF15 LD B,$04 B=04.
Draw_Tile_5 DF17 PUSH BC Stash BC on the stack.
DF18 LD A,($E75F) B=*Tile_Horizontal_Coordinate.
DF1B LD B,A
DF1C LD C,$07 C=07.
DF1E CALL Calculate_ScreenBlockAddress Call Calculate_ScreenBlockAddress.
DF21 LD A,$08 A=08.
DF23 PUSH HL Stash HL on the stack.
Draw_Tile_6 DF24 LD BC,$0003 BC=0003.
DF27 PUSH HL DE=HL (using the stack).
DF28 POP DE
DF29 INC DE Increment DE by one.
DF2A PUSH HL Stash HL on the stack.
DF2B LDDR LDDR.
DF2D INC HL Increment HL by one.
DF2E LD (HL),C Write C to *HL.
DF2F POP HL Restore HL from the stack.
DF30 INC H Increment H by one.
DF31 DEC A Decrease A by one.
DF32 JP NZ,Draw_Tile_6 Jump to Draw_Tile_6 until A is zero.
DF35 POP HL Restore HL from the stack.
DF36 CALL Calculate_AttributeAddress Call Calculate_AttributeAddress.
DF39 PUSH DE HL=DE (using the stack).
DF3A POP HL
DF3B INC DE Increment DE by one.
DF3C LD BC,$0003 BC=0003.
DF3F LDDR LDDR.
DF41 LD A,$00 Write 00 to *DE.
DF43 LD (DE),A
DF44 LD HL,$E75F HL=Tile_Horizontal_Coordinate.
DF47 INC (HL) Increment *HL by one.
DF48 POP BC Restore BC from the stack.
DF49 DJNZ Draw_Tile_5 Decrease counter by one and loop back to Draw_Tile_5 until counter is zero.
Draw_Tile_7 DF4B POP HL Restore HL and IX from the stack.
DF4C POP IX
DF4E DEC IX Decrease IX by one.
DF50 DEC IY Decrease IY by one.
DF52 POP BC Restore BC from the stack.
DF53 DEC B Decrease B by one.
DF54 JP NZ,Draw_Tile_0 Jump to Draw_Tile_0 until B is zero.
DF57 RET Return.
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