CG-1280 Rev. N 09/13 - General Dynamics SATCOM Technologies

Overview2.4.1.6 Dual Channel Resolver-to-Digital Converter PCB Assembly(Optional POL and 4TH AXIS)The Resolver-to-Digital Converter (RDC) PCB accepts analog inputs from theantenna-mounted resolvers (via the rear panel termination circuit card) and providesa binary digital encoded representation of the pointing angles for the POL and 4THAXIS to the CPU. VME bus interface circuitry is included, based upon CPU andRDC timing requirements. The standard configuration is for single-speed resolversand 16-bit encoding.2.4.1.7 IEEE-488 Interface (Optional)The IEEE-488 bus has been optionally incorporated into the 7200 ACU toaccommodate users wishing to utilize this type of interface. The IEEE-488 busallows connectivity between different programmable devices with a standardinterface for communications between each instrument. The IEEE-488 interface isalso known as GPIB (General Purpose Interface Bus) or HPIB (Hewlett PackardInterface Bus), and is electrically similar to IEC-625. Please refer to document CG-6041 for M&C protocol for this interface.2.4.1.8 Time and Frequency Processor Board (Optional)The 7200 ACU clock accuracy can be precisely maintained by utilizing the optionalTime and Frequency Processor Board. This VME board is used in conjunction withan external (CFE) time source to synchronize the 7200 ACU clock to the accuratetime source. The external time source sends an IRIG-B compliant signal to the J3BNC connector on the rear of the 7200 ACU. This signal is routed to the Time andFrequency Processor Board (TFP). The VCPU board acquires only the year fromthe on-board real-time clock while the rest of the time/date information is takendirectly from the TFP board. If the TFP board becomes disconnected from itssource, a message will be displayed on the ACU “External Timing Source Lost”.2.4.1.9 ACU Chassis AssemblyThe ACU is housed in a custom chassis assembly which mounts in a standard 19-inch Electronics Industry Association (EIA) rack, requiring 7-inches of vertical rackspace (4 Rack Units per EIA 310). The nominal overall dimensions of the ACUchassis are: 7-inches tall by 19-inches wide by 20-inches deep. The 7200 ACU’sweight is approximately 27 lbs. A four-slot VME card cage, which houses theVCPU, I/O, and RDC PCB’s, is mounted to the inside of the chassis top plate. Thetop plate is hinged at the rear of the chassis and includes a locking support arm tofacilitate convenient front-side access to the card cage. Studs connected to thefront panel support the front panel display and keypad and their respective controlcircuit cards.2-15