| 摘要 |
PURPOSE:To attach and replace a unit card without a special consideration related to an allocated address, and also to execute safely its operation by providing a priority determining means for selecting a card. CONSTITUTION:An address signal from an arithmetic unit 101 which has been loaded on a CPU card 100 is inputted to decoder circuits 130-133 attached to each unit card 120-123. They are collated with address values which have been set to address allocating switches 140-143, and in case of coincidence, its output signal Wn (n=0-3) becomes '1'. W0-W3 are returned once to a card inserting slot 110, and inputted to a priority determining circuit 115 for selecting a card. The priority determining circuit 115 for selecting a card is a circuit for generating gate signals X0-X3 by which the only signal is '1' by giving an optional priority to W0-W3, even in case plural signals have become '1' simultaneously with regard to the outputs W0-W3 of an address decoder of each unit card, and constituted of an encoder 113 and a decoder 114.
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