FDC data transfer end recognition control method and circuit in data access system

摘要

The data access system controls the end of data transfer between CPU and FDC with built-in DMAC to be recognized by FDC as simple software control. For this, a DMA request from the FDC sets a first port address, which is a DMA recognition port address, to the DMA port address, responds to the DMA request, sets a predetermined transfer count value according to the remaining sector amount of the floppy disk, Command to the FDC to access the data and to check the generation of an interrupt from the FDC to change the transfer count to a set value according to the current operation mode upon detecting an interrupt occurrence and to set the terminal count port address 2 port address to notify the FDC of the end of data transfer. A simple circuit and software control inform the FDC of the end of data transfer.