Z80 Sudoku – Row/Column/Box Scan Design

Board base address = $A000.

Row base = $A000 + row*9.

Column base = $A000 + col.

Box base = $A000 + (row/3)27 + (col/3)3.

Iteration Strategy

Row: increment pointer 9 times sequentially.

Column: increment pointer by 9 each step.

Box: nested 3×3 iteration using row stride of 9.