9914V TAPE UNIT

2.5 Digital Data Paths Board Description2.5.1 OverviewThis description applies to the DDP board, part number 123620.Data from the Pertec interface (IWDO - IWOP) is picked up by the DDP. to be encoded intothe desired format and sent to the AOP to be written to tape.When reading from tape, data from the AOP board is deskewed, decoded, checked forerrors and corrected if necessary. The data is then gated onto the Pertee interface with anaccompanying read strobe (IRSTR) for each data character.The actions of the DDP board at anyone time is controlled by the custom VLSI chips. Thiscontrol can be split into three basic types of operationa) initialisation,b) data transfers,c) diagnostics.2.5.2 InitialisationThe Data Control board notifies the OOP board of the recording density. which mayoriginate from• analysis of the tape's recorded density. or• the configuration byte settings, or• the power-on default, or• a host command.2.5.3 Write Data Transfers8,Ja, ""RITE OATA) ""RITE PARITY 4-5~ENCODERCONvERSION~PARITY1 '"CONTROL ~ ""RITE PE/NRZ 9 IJDOUT 0-7STATUS CONTROL ENCODER TO ADP( J. ,)FIGURE 2.5.3.1DDP WRITE BLOCK DIAGRAM95 124766 (Draft Issue A) PCB Descriptions2 - 20