Routines
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BB9E: Draw a 3x3 grid attribute color into attribute file if tile is background
Used by the routine at BC17.
Input
C Attribute color
HL Address into the attribute file
DE Address into the attribute buffer
BB9E CALL $BBA8 Draw a row of attribute color to attribute file
BBA1 CALL $BBA8 Draw a row of attribute color to attribute file
BBA4 CALL $BBA8 Draw a row of attribute color to attribute file
BBA7 RET
Draw a row of attribute color into attribute file
BBA8 LD A,(DE) Is attribute byte from attribute buffer a 'background' tile (black background -> $47 or blue background -> $0F)?
BBA9 CP $47
BBAB JP Z,$BBB3
BBAE CP $0F
BBB0 JP NZ,$BBB8
is a background tile
BBB3 LD A,(HL) Blend color attribute over background color
BBB4 AND $38
BBB6 OR C
BBB7 LD (HL),A
next tile
BBB8 INC HL Increment address into attribute file and buffer
BBB9 INC DE
BBBA LD A,(DE) Is attribute byte from attribute buffer a 'background'
BBBB CP $47
BBBD JP Z,$BBC5
BBC0 CP $0F
BBC2 JP NZ,$BBCA
is background tile
BBC5 LD A,(HL) Blend color attribute over background color
BBC6 AND $38
BBC8 OR C
BBC9 LD (HL),A
next tile
BBCA INC HL Increment address into attribute file and buffer
BBCB INC DE
BBCC LD A,(DE) Is attribute byte from attribute buffer a 'background'
BBCD CP $47
BBCF JP Z,$BBD7
BBD2 CP $0F
BBD4 JP NZ,$BBDC
is background tile
BBD7 LD A,(HL) Blend color attribute over background color
BBD8 AND $38
BBDA OR C
BBDB LD (HL),A
BBDC PUSH DE Save DE
BBDD LD DE,$001E Point address into attribute file and buffer to the next row
BBE0 ADD HL,DE
BBE1 POP DE
BBE2 PUSH HL
BBE3 LD HL,$001E
BBE6 ADD HL,DE
BBE7 EX DE,HL
BBE8 POP HL
BBE9 RET
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