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hilda output it is called hold acknowledge signals it is active high i e it goes high when microprocessor receives hold
hold inputthis signal when goes high indicates that other device such as dma controller is requesting the use of address and
ready inputmicroprocessor has to communicate with other peripherals which are slow as compared to the microprocessor ready
externally initiated signalsother than interrupt there are followings externally initiated signals available in 8085
interrupt signalsthere are five interrupt signals in 8085 microprocessor these signals are used to inter rut the current
power supply and clock frequency there are following pins for power supply and clock frequency signalsvcc 5 v power
status signals there are three status signals iom s and s1 all these signals are output signalsio m - it is a status
control signalsthere are two control signals and one special ale in this category all these signals are output
multiplexed address data bus pins ad7 - ad are used for multiplexed address data bus this bus is bidirectional input output and serves
higher order address bus the 8085 microprocessor has 8 pins dedicated to higher order address a15 - a8 these pins are used to
basic operations of 8085 microprocessor the 8085 microprocessor performs followings five basic operations 1 opcode fetch reading
control busthe control bus comprises of various single lines that carry various control signals for synchronizing
data busthe data bus is the group of 8 bit used to carry data there line are bidirectional data can flow in both
port addressthe port address is of 8 bit it is range from 00h to ffh it means there may be total i 256 input ports and
memory addressthe memory address is of 16 bits it ranges from 0000h to fffh 16bits address lines of 8085 microprocessor are
address busthe address bus is the group of 16 lines it is used to carry the address of memory location and addresses of
stack pointer spit is also a 16 bit register and a memory pointer similar to program counter it holds the memory address of
program counter pcit is a 16 bit register it is a memory pointer it stores the memory address of the next byte of the
carry fla registers the size of the accumulator is of 8 bit if after any arithmetical or logical operation 9th bit is
parity flag - registers if after any arithmetical or logical operation if number of the accumulator are even parity
auxiliary carry fla - registers if carry is generated from d3 to d4 in the accumulator after any arithmetical or logical operations
zero flag - registers if the result of any arithmetical or logical operation in the accumulator is zero i e all the bits
addition of binary numbers example add 110010102 -510 and 000001012510solution
representation of negative number as mentioned in chapter 1 in 8085 negative numbers are represented in 2 complement form and
sing flagif d7 bit left most bit of accumulator which some exceptions is 1 as a result of any arithmetical or