| 摘要 |
PURPOSE:To remove a memory area having no address specification by specifying the same product item line by two decoders individually, and simultaneously changing the array of output bits from a microprogram counter for specifying a control word consisting of two words or more by one line. CONSTITUTION:A certain address area in an input address 10 selects the 1st decoder 22 and other areas select the 2nd decoder 23. The control word consisting of four words specified by one product item line specified by the decoder 22 is selected by counting up the lower four bits 19 of a counter output successively from the LSB14 of the four bits 19. Even if the counting is ended at two words out of the four words, the unused two words in the upper addresses can be used effectively as the two words of the lower addresses by selecting the product item line 12 again by the decoder 23 because the upper/lower positions of the lower four bits of the counter output is reversed against the specification by the decoder 22.
|
