Solution:

The following diagram can give you an overview about the data access procedure between Host PC and PCL-844 series: Host PC <==> memory address (ex. C800) <==> memory mapping to on-board dual port RAM <==> on-board processor <==> multi-port channels From the above structure, you can understand the communication bridge between Host PC and PCL-844 is dual port RAM, the received data will be stored in dual port RAM via on-board processor, then Host PC decodes and reads data from dual port RAM via the special driver, that means you don't need to know the real I/O address for each port of PCL-844 because on-board processor and the special driver will help you to handle it.