VDU Base      : $8000
VDU Register 0: $8800
VDU Register 1: $8C00

Initialize:
8800: 00
8C00: 00

Fill data:
8800: 00
8000: 00 00 00 00 00 00 00 00
8800: 01
8000: 01 01 01 01 01 01 01 01
8800: 02
8000: 02 02 02 02 02 02 02 02
8800: 03
8000: 03 03 03 03 03 03 03 03
8800: 00
8C00: FF
8000: 8C 8C 8C 8C 8C 8C 8C 8C

Verify
8800: 00
8C00: 00
8000.8007
 -> 00 00 00 00 00 00 00 00
8800: 01
8000.8007
 -> 01 01 01 01 01 01 01 01
8800: 02
8000.8007
 -> 02 02 02 02 02 02 02 02
8800: 03
8000.8007
 -> 03 03 03 03 03 03 03 03
8800: 00
8C00: FF
8000.8007
 -> 8C 8C 8C 8C 8C 8C 8C 8C