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Routines |
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Used by the routine at InitialiseGame.
Builds the tables that the game needs before it can start. First it makes the tables at ShiftTables of every byte shifted two, four and six bits to the right, as a pair of bytes. A page holds the first byte of every shifted value and the page after holds the second byte. Then it builds the shape tables with BuildShapeTables and the table of reversed bytes with BuildReverseTable.
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| BuildTables | F86B | LD HL,$FA00 | The shift tables. | |
| F86E | LD B,$02 | B=02. | ||
| BuildTables_Shift | F870 | LD C,$00 | Clear C. | |
| BuildTables_Byte | F872 | LD D,C | D=C. | |
| F873 | LD E,$00 | Clear E. | ||
| F875 | LD A,B | A=B. | ||
| BuildTables_Bits | F876 | SRL D | Shift D right. | |
| F878 | RR E | Rotate E right through the carry. | ||
| F87A | DEC A | Step A back. | ||
| F87B | JR NZ,BuildTables_Bits | Jump to BuildTables_Bits if the zero flag is clear. | ||
| F87D | LD (HL),D | Write D where HL points. | ||
| F87E | INC H | Advance H. | ||
| F87F | LD (HL),E | Write E where HL points. | ||
| BuildTables_Buffer | F880 | DEC H | Step H back. | |
| F881 | INC HL | Advance HL. | ||
| F882 | INC C | Advance C. | ||
| F883 | LD A,C | A=C. | ||
| F884 | AND A | Jump to BuildTables_Byte if A is not zero. | ||
| F885 | JR NZ,BuildTables_Byte | |||
| F887 | INC H | Advance H. | ||
| F888 | INC B | Advance B. | ||
| F889 | INC B | Advance B. | ||
| F88A | LD A,B | A=B. | ||
| F88B | CP $08 | Jump to BuildTables_Shift if A is not 08. | ||
| F88D | JR NZ,BuildTables_Shift | |||
| F88F | CALL BuildShapeTables | Call BuildShapeTables. | ||
| F892 | JP BuildReverseTable | Jump to BuildReverseTable. | ||
| Prev: F856 | Up: Map | Next: F895 |