| 摘要 |
PURPOSE:To discriminate the position of a write error of data written on an external storage medium in type unit basis, by executing a byte-by-byte parity check in addition to a check on period redundancy check codes. CONSTITUTION:When a microprocessor unit MPU1 sends a read-after-write command, the operation of a direct memory access DMA controller 5 is inhibited. Then when a read instruction is generated, data in a main storage device 2 is read to a common bus 6 and a disk controller 7 reads data on a floppy disk 3 to a parity generating and comparing circuit 9. Further, parity bits in data from the device for checking period redundancy check (CRC) codes are stored in a parity memory 8. The circuit 9 generates a parity bit for every bytes of the data from the disk 3. This parity bit is compared with the parity of data of the device 2 sent from the memory 8 and when they do not coincide with each other, an error is reported to the MPU1. |
