Skool Daze Routines
27008: Update SRB for column of character sprite
Called by the routine at 25008, which modifies the instruction at 27015 (SET n,(HL)) appropriately beforehand.
DE Base address of character UDG references
HL SRB address corresponding to top row of character sprite (32524-32607)
27008 LD B,4 There are 4 rows in a character sprite
27010 LD A,(DE) Pick up a character UDG reference
27011 INC D Next row of the character sprite
27012 AND A Is this the blank UDG?
27013 JR Z,27017 Jump if so (no need to update this SRB byte)
27015 SET n,(HL) Set the appropriate bit in the SRB byte; this instruction is modified by the routine at 25008 before this routine is called
27017 LD A,4 Point HL to the byte of the SRB corresponding to the next row of the screen
27019 ADD A,L
27020 LD L,A
27021 DJNZ 27010 Jump back until all 4 squares in the column are done
27023 BIT 3,D Return with the zero flag reset if we have just updated the SRB for the right column of the character sprite
27025 RET