Anordnung zum Einschreiben oder Auslesen von Datenfeldern in Datenmaschinen

摘要

1,177,021. Indirect addressing. TELEFONAKTIEBOLAGET L. M. ERICSSON. 28 March, 1967 [25 March, 1966], No. 14177/67. Heading G4A. An indirect addressing scheme in a computer uses a stored table of addresses associated with stored indications of field lengths in different memory blocks. A first instruction accesses a data memory to obtain the number of a connection device (electromagnetic relays) in a telephone network, the number being then placed in a register specified by two bits of a second instruction. Eight further bits of the second instruction are added to 0000000100000000, the result being used to address the data memory to obtain a word in a table therein. Twelve bits of this word, with 0000 following them, constitute the base address of a data memory block containing information about the connection device among others, and the other four bits of the word specify the number of bits (always a non- ,negative integral power of 2) devoted to each connection device in this block. The device number (see above) is shifted under control of these latter four bits (thus effectively multiplying it) to obtain the relative word address of the connection device information with the block. The relative address is added to the base address referred to the word part of the result being placed in a register specified by two further bits of the second instruction (see above), the address of the device field within the word being retained in the arithmetic unit. A third instruction uses the word part to address the data memory and the field-withinword part to select the connection device information from the word thereby read from the data memory.