| 摘要 |
PURPOSE:To reduce the number of lines required for the selection of I/O cards and to select a specific I/O card by connecting the I/O card on the basis of daisy chain connection and executing a specific sequence on the basis of an absolute address. CONSTITUTION:If the number of contacts of an I/O card when a bus line 5 is 8 bits, the address is latched after four clocks. Thus, the address values of all the I/O cards, i.e. the absolute addresses, are latched in each I/O card. At the service of a normal I/O card, i.e. at the execution of a normal sequence, data are transmitted to all the I/O cards sequentially on the basis of the daisy chain system. If data are to be transmitted to a certain I/O card, the address value of the I/O card to be transmitted is sent to a bus line at first, so that a data latch part of the I/O card corresponding to the address value assigned at the ON of power supply corresponds to the address value and only the I/O card is turned to transmissible status. |
