UNIT-III Pin Diagram Of 8086 Minimum Mode And Maximum Mode Of Operation. Timing Diagram Memory Interfacing To 8086 (Static RAM & EPROM). Need For DMA. DMA Data Transfer Method. Interfacing With 8257.

Fig 3.1 Pin diagram of 8086

Fig 3.2 Minimum mode pin diagram of 8086 Minimum mode of 8086 • When the Minimum mode operation is selected, the 8086 provides all control signals needed to implement the memory and I/O interface. Fig 3.2 Minimum mode pin diagram of 8086

Fig 3.3 Write cycle timing diagram of 8086 in Minimum mode

Fig 3.4 Maximum mode 8086 system 8086 in Maximum mode Fig 3.4 Maximum mode 8086 system

Fig 3.5 General bus operation cycle in Maximum mode

Memory interfacing Fig 3.6 Address mapping

Fig 3.7 Memory interfacing to 8086

DIRECT MEMORY ACCESS For the applications that require huge amounts of data transfer to memory from a magnetic or optical disk a dedicated hardware device called DMA controller is used. The DMA controller temporarily borrows the address bus ,data bus and control bus from the microprocessor and transfers the data bytes directly from the disk controller to a series of memory locations. Some DMA devices even can do memory to memory transfers.

Fig 3.8 Block diagram of DMA Interfacing

Fig 3.9 Block diagram that shows DMA data transfer scheme

Fig 3.10 Pin diagram of 8257 DMA controller

Fig 3.11 Functional block diagram of 8257

Fig 3.12 Mode set register Bit format Fig 3.13 Status register Bit format

Table 3.1 8257 Register selection

Fig 3.14 Interfacing 8257 with 8086