|-
!I/O port address
!b1
!b0
!Function
!Read/Write
|-
|&BCxx||0||0||Select 6845 register||Write only
|-
|&BDxx||0||1||Write to selected internal 6845 register||Write only
|-
|&BExx||1||0||(note 1)||Read only
|-
|&BFxx||1||1||Read from selected internal 6845 register||Read only
|-
|}