| 摘要 |
<p>1508476 Program jumps NIXDORF COMPUTER AG 23 April 1975 [24 April 1974] 16852/75 Heading G4A The addresses for addressing a section 22 of a store 20 containing instructions, each of two words, are generated by an arithmetic unit 27 adding the contents of registers 28, 29 and are passed to an address register 25 via an instruction address register R7 the output of which is also supplied to register 28. During normal operation register 29 receives the constant 2 via gate 31 whereas for a jump instruction a jump address increment is supplied to register 29 from store 20 via gate 32, controlled by a microprogram control unit 34, and added to the contents of R7. As the instructions are stored in store 20 only at even addresses the least significant bit in the address from arithmetic unit 27 is not stored in instruction address register R7 but is used to indicate, when it is 1, that a subprogram jump is to take place, this being detected by an AND gate 33 which supplies a signal to microprogram control unit 34 to cause the address in a stack index register R6 to be incremented by 2 via arithmetic unit 27 and this address is used to address a return address stack 24 in store 20 to store a return address. The subprogram is then carried out by addressing a subprogram in section 23 of store 20. Data addresses are fed to address register 25 via a gate 37, the data being stored in section 21 of store 20.</p> |
