Patent GB-1504096-A (GB)
Title: Digital processor
IPC: G06F19/00
Filed: 1976-03-19
Abstract: 1504096 Digital data processors RAYTHEON CO 19 March 1976 [21 April 1975] 11226/76 Heading G4A A digital data processor comprises a macroinstruction memory (not shown) storing a repertoire of macroinstructions, a microinstruction memory CM storing sets of microinstructions, each set corresponding to a respective macroinstruction, a register CMO storing a digital control word, a source decoder coupling data to an input bus IB from one of a plurality of data sources selected in accordance with a part S of the digital control word, an arithmetic section (not shown) processing the data on the input bus in accordance with a part F of the digital control word and coupling the processed data to an output bus (not shown), a destination decoder for coupling the processed data on the output bus to one of a plurality of data destinations selected in accordance with a part D of the digital control word, a condition selector coupled to the register CMO and to a plurality of binary signal sources U, A N , ... , SGN and coupling on to a condition true line C T  one of the plurality of binary signal sources selected in accordance with a part C of the digital control word, gates for enabling or inhibiting the processed data to pass to the selected one of the plurality of data destinations in accordance with the value of the signal on the condition true line, a plurality of bi-stable flip-flops (not shown) storing status signals, and a flip-flop selector (not shown) coupling a selected one of the plurality of bi-stable flip-flops to the condition selector to serve as one of the plurality of binary signal sources. The processor may be used in an airborne missile, the data sources and destinations including the macroinstruction memory, a data memory (DM, not shown), the microinstruction memory CM, and gyros, accelerometers and control surface actuators incorporated in the missile. The data memory DM may be directly or indirectly addressed. The digital control word may be transferred in parallel form into the register CMO from the microinstruction memory CM during normal operation of the processor, or may be transferred in serial form into the register CMO from external test equipment during testing of the processor prior to launching the missile. The microinstruction memory CM receives an address from (1) the operation code (OP) of the current macroinstruction, or (2) a JUMP field (J) of the current microinstruction, or (3) the incremented contents of an address register CMAR, or (4) the fixed, predetermined contents of a register W, utilized when a program interruption occurs. The JUMP field may alternatively be used as a data source in which case the next sequential microinstruction address is selected to obtain the next microinstruction or to indicate that the last microinstruction of a set of microinstructions is in the register CMO. A control/ operation filed (C/O) of the current microinstruction specifies a control operation to be performed concurrently with the source field (S), function field (F) and destination field (D) operations. The plurality of bi-stable flip-flops is set and reset by signals SNS1, SNS0 derived from the control/operation field of the current microinstruction, and by signals from external sources, e.g. from a pulse generator actuated on launching the missile. The resetting of one of the flip-flops causes a macroinstruction to be skipped by incrementing twice a program counter register. During testing of the processor using the external test equipment, the result of a calculation performed using a test microinstruction loaded serially into the register CMO is analysed. Such a test microinstruction may be read as the next test microinstruction is being loaded into the register CMO. The number of macroinstructions executed during the test may be recorded by counting the number of "last microinstruction" indications obtained from the JUMP fields of the corresponding microinstructions.