1.

DMA In a minimum mode (MN/MX’)

Answer»
  • The direct memory access in minimum mode is facilitated by HOLD and HLDA signals. 
  • When the external devices wants access the memory directly it request through a high signal at HOLD pin. 
  • The 8086 microprocessor samples the HOLD signal at low high transition of clock. 
  • The 8086 microprocessor acknowledge the holds request by making the HLDA (HOLD Acknowledgement) high at the end of current bus cycle. 
  • The external device accesses the memory and after completion of task it withdraw the HOLD request by making the signal at HOLD pin low. 
  • The 8086 microprocessor check the HOLD pin at every low to high transition of clock .After detecting the low signal at HOLD it will make the signal at HLDA low.


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