OPERATING MODES OF 8259A

!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } 1.Fully Nested Modes .Default mode. .IR0 has the highest priority and IR7 has the lowest one. .If the ISR (in service) bit is set, all the same or lower priority interrupts are inhibited. 2.End Of Interrupt .The ISR bit can be reset either with AEOI bit of ICW1 or by EOI command. .Two types of EOI command; a)Specific b)Non-specific .The non-specific EOI command automatically reset the highest ISR bit. .When a mode that may disturb the fully nested structure, the...

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CISC AND RISC

!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } CISC:- Acronym for Complex Instruction Set Computer. They are chips that are easy to program and which makes efficient use of m/y. “High level” instruction set Executes several “low level operations” Ex: load, arithmetic operation,m/y store. Used in most common Intel 80x86 and Motorola 68k series. FEATURES OF CISC:- Extensive instructions. Complex and efficient machine instructions. Extensive addressing capabilities for m/y operations. Microending ...

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DESIGN OF A PC BASED MULTIMICROPROCESSOR SYTEM

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INTERFACING I/O PORTS

!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } I/O ports are devices through which the microprocessor (µP) communicates with other devices or external data sources /destination INPUT ACTIVITY: The activity that enables the MP to read data from external devices Eg: keyboard, joystick, mouse OUTPUT ACTIVITY: Transfers from the MP to the external devices. Eg: CRT-display, 7-segment display, printers etc. INPUT DEVICES: Feed data into a MP system OUTPUT DEVICES: Accept data from a MP system That is for MP...

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STEPS IN INTERFACING AN I/O DEVICE

Steps performed to interface a general I/O device with a CPU  Connect the data bus of the MP system with the data bus of the I/O port.  Derive a device address pulse by decoding the required address of the device & use it as the chip select of the device.  Use a suitable control signal ie, IORD & IOWR to carry out device operations. METHODS OF INTERFACING I/O DEVICES Two methods I/O MAPPED I/O & MEMORY MAPPED I/O  I/O MAPPED I/O  Devices are viewed as distinct I/O devices accordingly  All the available address...

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INSTRUCTION EXECUTION TIMING

Minimum Mode 8086 System • In a minimum mode 8086 system, the microprocessor 8086 is operated in minimum mode by strapping its MN/MX pin to logic 1. • In this mode, all the control signals are given out by the microprocessor chip itself. There is a single microprocessor in the minimum mode system. • The remaining components in the system are latches, transreceivers, clock generator, memory and I/O devices. Some type of chip selection logic may be required for selecting memory or I/O devices, depending upon...

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8086 Instruction Set Summary

The following is a brief summary of the 8086 instruction set: Data copy/transfer Instructions These type of instruction are used to transfer data from source operand to destination operand. All the store, move, load, exchange, input and output instructions belong to this category. a) Memory/Register Transfers LDS Load pointer using data segment LES Load pointer using extra segment MOV Move byte or word to register or memory XCHG Exchange byte or word XLAT Translate byte using look-up table b) Stack Transfers ...

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The 8086 Addressing Modes

- 8086 memory addressing modes provide flexible access to memory, allowing you to easily access variables, arrays, records, pointers, and other complex data types. -12 addressing modes classified in 5 groups i ) Addressing modes for register and immediate data 1. Register addressing -the instruction will specify the name of the register which holds the data to be operated by the instruction -ex: MOV CL, DH : content of 8-bit DH...

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