The base port is for control and status, the second port for command and data trans-fer, and the third port for interrupt flags.I/O Port Interface Bit DefinitionPort Address = Base + 0WRITE: Control Register READ: Status RegisterBit 7 Hard Reset (HRST) Bit 7 Self Test in Progress (STST)Bit 6 Soft Reset Bit 6 Internal Diagnostic Failure (DIAGF)Bit 5 Interrupt Reset (IRST) Bit 5 Mailbox Initialization Required(INIT)Bit 4 SCSI Bus Reset (SCRST) Bit 4 SCSI Host Adapter Idle (IDLE)Bit 3 Reserved (0) Bit 3 Command/Data Out Port Full (CDF)Bit 2 Reserved (0) Bit 2 Data In Port Full (DF)Bit 1 Reserved (0) Bit 1 Reserved (Undefined)Bit 0 Reserved (0) Bit 0 Invalid H A Command (INVDCMD)Port Address = Base + 1WRITE: Command/Data Out READ: Data InBit 7 Command/Data Out Bit 7 Bit 7 Data In Bit 7Bit 6 Command/Data Out Bit 6 Bit 6 Data In Bit 6Bit 5 Command/Data Out Bit 5 Bit 6 Data In Bit 6Bit 4 Command/Data Out Bit 4 Bit 4 Data In Bit 4Bit 3 Command/Data Out Bit 3 Bit 3 Data In Bit 3Bit 2 Command/Data Out Bit 2 Bit 2 Data In Bit 2Bit 1 Command/Data Out Bit 1 Bit 1 Data In Bit 1Bit 0 Command/Data Out Bit 0 Bit 0 Data In Bit 0Port Address = Base+ 2WRITE: Reserved, do not write READ: Interrupt FlagsBit 7 Bit 7 Any InterruptBit 6 Bit 6 ReservedBit 5 Bit 5 ReservedBit 4 Bit 4 ReservedBit 3 Bit 3 SCSI Reset Detected (SCRD)Bit 2 Bit 2 HA Command Complete (HACC)Bit 1 Bit 1 MBO Available (MBOA)Bit 0 Bit 0 MBI Full (MBIF)adaptec AHA-1740A/1742A/17444-2
