| 摘要 |
PURPOSE:To reduce deterioration in the processing ability of a system in case of the occurrence of overrun, by storing a data transfer break point temporarily when the overrun is detected, then restarting data transfer at the break point thereafter. CONSTITUTION:A counter generates an overflow signal 34 in an input/output control starting sequence when the permissible time of single unit data transfer is elapsed, and a main control part 10 inputs the signal 34 to generate selection signals 32 and 33. A gate 16 is opened by the signal 32 and the current address information of a magnetic drum is inputted from a data bus 30 and stored in a register 12 temporarily. Further, a gate 17 is opened to store a starting address in the register 12 temporarily. On the other hand, the magnetic drum device still rotates thereafter and its address information is stored in an address buffer register 13 temporarily. A coincidence comparing circuit 15 compares the contents of the registers 12 and 13 with each other and when coincidence is obtained, the contents of one unit data in an address at this time are sent to and written on the magnetic drum device. Then, the data restarts at this address. |
