| 摘要 |
PROBLEM TO BE SOLVED: To provide a data transfer apparatus that transfers/receives an HB (Heart Beat) packet not through a microcomputer during data transfer between a DMA bus and an IEEE 1394 serial bus. SOLUTION: Upon receipt of occurrence of underflow from an HB timer 9, an HB controller 11 gives an temporary interrupt instruction of automatic transmission processing to a DMA control circuit 8, creates an HB notice packet after confirming the interruption, gives the packet to a transmission buffer 2, and gives an automatic transmission processing restart instruction to the DMA control circuit when the packet from a reception packet 3 is an HB reception confirmation packet. Further, a reception filter 4 checks a reception packet of the reception buffer, and when the packet is addressed to a microcomputer 102, the reception filter 4 gives the packet to the microcomputer 102, and when the packet is addressed to a DMA bus 103, the reception filter 4 gives the packet to the DMA bus. When the packet is an HB reception acknowledgement packet with respect to the HB notice packet sent from the DMA bus at temporary interruption of automatic transmission processing of transmission parallel data, the reception filter gives the packet to the HB controller.
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