EINRICHTUNG ZUM DYNAMISCHEN STEUERN DER AUSTAUSCHSTELLENZAHL BEI DIREKTEM ZUGRIFF

A device for dynamic DMA transfer sizing, which finds application in 16-bit computers and microprocessor systems including 8-bit devices enables the performance of DMA byte and word transfer operations. The type of the DMA operation is automatically determined during the transfer in dependance upon an 8-bit-DMA-controller 7 word transfer determining output 15 and signals 25, 27 indicating the bit-widths of memory modules 5, 10 and 3 and of input-output devices 6, 11 and 4 for an arbitrary number of transferred bytes and arbitrary start memory address. The 16-bit data bus 2, 9 of the 16-bit microprocessor system 1 is converted into an 8-bit data bus for byte transfer operation, whereupon the 8-bit DMA controller 7 adjusts its counter by one. For word transfer operation the 16-bit data bus of the microprocessor system 1 is not converted into an 8-bit bus and the 8-bit DMA controller adjusts its counters by two. Advantages of the invention are that the transfer number of digits is automatically determined at the beginning of the transfer operation and is not restricted by the parity of the byte count and start address.