| 摘要 |
PURPOSE:To decrease the overhead due to the general polling by providing the register showing the pressence or absence of the data request within the terminal control unit along with the function to store and then fetch the addresses of the terminal units requesting the data one by one. CONSTITUTION:General polling signal GP is transmitted from the CPU to terminal control unit TCE containing terminal units T1-Tn, and unit TCE received signal GP finds out the terminal having the data transfer request among units T1-Tn to give the answer to the CPU. Then the following units are provided to unit TCE: command register 71 showing the presence or absence of the data request given from units T1-Tn; address cutter 73 which gives queuing to the addresses of units T1- Tn; and status production circuit 72 which checks the contents of register 71 with reception of signal GP from the CPU respectively. Then the address signal is transferred to the CPU in the form of the answer signal of signal GP or the signal with the message, thus reducing the overhead caused by signal GP. |
