microprocesser 8085

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applications

Thousands of items that were traditionally not computer-related includemicroprocessors. These include large and small householdappliances,cars (and their accessory equipment units), car keys, tools and test

instruments, toys, light switches/dimmers and electrical circuit breakers,smoke alarms, battery packs, and hi-fi audio/visual components(from DVD players to phonograph turntables.) Such products as cellular telephones, DVD video system and ATSC HDTV broadcast systemfundamentally require consumer devices with powerful, low-cost,microprocessors. Increasingly stringent pollution control standardseffectively require automobile manufacturers to use microprocessor enginemanagement systems, to allow optimal control of emissions over widelyvarying operating conditions of an automobile. Non-programmable controls

would require complex, bulky, or costly implementation to achieve theresults possible with a microprocessor

Generally a computer organization is as follows INPUT> ALU+CONTROL UNIT+MEMORY> OUTPUT

(1) (2)

(3) Unit 2 is generally replaced with microprocessor. So a microprocessor can be

represented as : Microprocessor=ALU+Registers+Program Counter+Control and

Timing circuit+Stack Pointer +Interrupt Circuit. The hardware of the 8085 microprocessor can be easily understood from the

description of the programming model.



Pin configuration:

8085 pin diagram

8085 programming model: REGITERS:

There are six general purpose registers available, Each can store 8bit

data. They are denoted as B,C,D,E,H,L. If one need to store 16 bit of data

they the registers can be paired the pairing is like BC,DE and HL.

Intel 8085 microprocessor



ACCUMULATOR: It is a 8bit register, It is also a register but the difference is that it is part of

a Arithmetic and Logical unit(ALU).The result of every operation that has been

carried out are stored in the Accumulator. It is generally denoted as ³A´ or

³ACC´. FLAGS: There are 5 flipflops which act as flags. Their operation upon their condition

i.e. either SET or RESET, this condition is determined by the output of the

ACCUMULATOR. Those flags are namely: Sign(S) : This is SET when the D7 bit is 1 else it is RESET Zero(Z): When the output is zero it is SET else RESET

Auxiliary carry(AU): When the D3 bit has has a carry, it is pushed to the D4bit, then the AU is SET else RESET Parity(P): It is SET when the Number of 1s are even and RESET when the

number of 1s are odd. Carry(C): It is SET when the D0bit has carry else RESET. Positions D1,D3 and D5 are generally Zero. Program Counter: It is 16bit register. It is used to sequence the execution of instructions to the

memory address from which the next bte or data has to be fetched. Stack Pointer: It is also 16 bit register. It points to the memory location in th R/W operation. It

Is generally associated with subroutines(seen in later posts) Address Bus: It ranges from A15 to A0. They are divided in the two parts containing A15 to

A8 as higher order bit, and they are unidirectional in operation i.e. address

can be destined from microprocessor to peripheraldevices and other way is

not possible .And the second part containing AD7 to AD0, they are generally

called as Multiplexed Address/Data lines. They are bidirectional and used to

represent the lower order address/data lines. Control and Status Signal: Two signals RD/WR. Three status signals io/m s1,s0 and special signal called

Address enable latch(ALE).



ALE: It is used to separate the multiplexed Address/Data lines into lower

order address line(A7A0) and data lineD7D0.A positive going pulse is

generated every time the 8085 begins operation. RD: Active low, Indicates that memory device is ready to be read. WR: Active low, Indicates that data on the data bus are ready too be written. IO/M: Differentiate between I/O operation and memory operations. HIGH :I/O operation is carried on. LOW: Memory operation is carried on. s1,s0:Similar to IO/M but are rarely used. Timing Circuit: X1,X2: Crystal oscillator is connected to these pins X1,X2 they need to be at

3MHz frequency for the operation, so input of 6MHz is to be given CLK OUT :The output from this port can be used as system clock for other devices. READY: When High, Microprocessor start to proceed the process provided by

the Input/output devices and memory device. HOLD: When it is high. It means that some process is already in progress and

it suspends all other process. HOLDA: The above status is indicated by providing HOLDA(HOLD

Acknowledge) as High. All the process can be processed only when Hold is

low.

RESETIN: Reset the microprocessor. It is active low. RESETOUT: Output is obtained when High. INTERRUPT: INTR: Interrupt signal to microprocessor. It is required to provide the location

the location of ISR(Interrupt service routine). INTA: when microprocessor receives an interrupt request on INTR, this is

acknowledged by sending a low signal to INTA. RST 7.5,RST 6.5,RST5.5: Provide interrupt signal to microprocessor with

hardware generated by vectoring to ISR .Priority order 7.5>6.5>5.5. they have

higher priority that INTR.



TRAP: Nonmaskable interrupt and has the highest priority during execution.

Above content is not only the programming model of 8085Microprocessor,

but most of the pins of the processor can also be understood. This will enable

you to understand programming of the processor which will be dealt in

upcoming posts

MICROPROCESSER

CPU is designed to perform the arithmetic and logical operations inside

the computer. Common operations inside the computer include adding,

subtracting, multiplying, comparing the values and fetching the differentnumbers to process them. The higher the CPU clocks¶ speed the more

efficient will be the performance of the computer.

Computer¶s performance is also influenced by the system bus

architecture, memory used, type of the processor and software program

being running. Pentium 4 is the fastest type of the Intel¶s processor that

contains 125,000,000 transistors and operates at the speed of 3.6 GHz.



A microprocessor incorporates the functions of a computer 's central processing unit (CPU) on a single integratedcircuit,[1] (IC) or at most a few integrated circuits.[2] It is amultipurpose, programmable device that accepts digital data as

input, processes it according to instructions stored in its memory,and provides results as output. It is an example of sequentialdigital logic, as it has internal memory. Microprocessors operateon numbers and symbols represented in the binary numeralsystem.

The advent of low-cost computers on integrated circuits has transformed

modern society. General-purpose microprocessors inpersonal

computers are used for computation, text editing, multimedia display, and

communication over the Internet. Many more microprocessors are partof embedded systems, providing digital control of a myriad of objects from

appliances to automobiles to cellular phones and industrial process control.

microprocesser 8085

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