01-09-2012, 11:06 AM
Intel 8085 Microprocessors
Intel 8085.doc (Size: 134 KB / Downloads: 734)
Organization of Intel 8085 Microprocessors:
The microprocessors that are available today came with a wide variety of capabilities and architectural features. All of them, regardless of their diversity, are provided with at least the following functional components, which form the central processing unit (CPU) of a classical computer .
a) Register Section: A set of registers for temporary storage of instructions, data and address of data.
b) Arithmetic and logic unit: Hardware for performing primitive arithmetic and logical operations.
c) Interface Section: Input and output lines through which the microprocessor communicates with the outside world.
d) Timing and control Section: Hardware for coordinating and controlling the activities of the various sections within the microprocessor and other devices connected to the interface section.
The block diagram of the microprocessor along with the memory and input / output (I/O) devices is shown in the figure.
Intel Microprocessors:
Intel 4004 is the first 4-bit microprocessor introduced by Intel in 1971. After that Intel introduced its first 8-bit microprocessor 8088 in 1972.
These microprocessors could not last long as general-purpose microprocessors due to their design and performance limitations.
In 1974, Intel introduced the first general purpose 8-bit microprocessor 8080 and this is the first step of Intel towards the development of advanced microprocessor.
After 8080, Intel launched microprocessor 8085 with a few more features added to its architecture, and it is considered to be the first functionally complete microprocessor.
The main limitations of the 8-bit microprocessors were their low speed, low memory capacity, limited number of general purpose registers and a less powerful instruction set .
To overcome these limitations Intel moves from 8-bit microprocessor to 16-bit microprocessor.
In the family of 16-bit microprocessors, Intel’s 8086 was the first one introduced in 1978 .
8086 microprocessor has a much powerful instruction set along with the architectural developments, which imparted substantial programming flexibility and improvement over the 8-bit microprocessor.
Instruction and data formats :
Memory used in the Intel 8086 microprocessor is organized in 8-bit , i.e. It is byte organized .
Every byte has a unique location in physical memory .
The address bus of 8085 is 16-bit wide , so the location of memory is described by one of a sequence of 16-bit binary address .
The 8085 can address up to 64k(i.e. 65,535) bytes of memory , which may consist of both RAM and ROM .
Addressing Modes :
The 8085 has four different modes for addressing data stored in memory or in registers –
Direct : Bytes 2 and 3 of the instruction contains the exact memory address of the data item( the low-order bits of the address are in byte 2 , the high-order bits in byte 3 )
Register : The instruction specifies the register or register pair in which the data are located .
Register Indirect : The instruction specifies a register pair which contains the memory address where the data are located .( the high-order bits of the address are in the first register of the pair and the low order bits in the second ).
Immediate : The instruction contains the data itself . This is either and 8-bit quantify or a 16-bit quantify (least significant byte first , most significant byte second ).
Unless directed by and interrupt or branch instruction the execution of instructions proceeds through consecutively increasing memory locations.
A branch instruction can specify the address of the next instruction to be executed in one of two ways -
Direct: The branch instruction contains the address of the next instruction to be executed .
Regular Indirect : The branch instruction indicates a regular pair which contains the address of the next instruction to be executed .
Intel 8085.doc (Size: 134 KB / Downloads: 734)
Organization of Intel 8085 Microprocessors:
The microprocessors that are available today came with a wide variety of capabilities and architectural features. All of them, regardless of their diversity, are provided with at least the following functional components, which form the central processing unit (CPU) of a classical computer .
a) Register Section: A set of registers for temporary storage of instructions, data and address of data.
b) Arithmetic and logic unit: Hardware for performing primitive arithmetic and logical operations.
c) Interface Section: Input and output lines through which the microprocessor communicates with the outside world.
d) Timing and control Section: Hardware for coordinating and controlling the activities of the various sections within the microprocessor and other devices connected to the interface section.
The block diagram of the microprocessor along with the memory and input / output (I/O) devices is shown in the figure.
Intel Microprocessors:
Intel 4004 is the first 4-bit microprocessor introduced by Intel in 1971. After that Intel introduced its first 8-bit microprocessor 8088 in 1972.
These microprocessors could not last long as general-purpose microprocessors due to their design and performance limitations.
In 1974, Intel introduced the first general purpose 8-bit microprocessor 8080 and this is the first step of Intel towards the development of advanced microprocessor.
After 8080, Intel launched microprocessor 8085 with a few more features added to its architecture, and it is considered to be the first functionally complete microprocessor.
The main limitations of the 8-bit microprocessors were their low speed, low memory capacity, limited number of general purpose registers and a less powerful instruction set .
To overcome these limitations Intel moves from 8-bit microprocessor to 16-bit microprocessor.
In the family of 16-bit microprocessors, Intel’s 8086 was the first one introduced in 1978 .
8086 microprocessor has a much powerful instruction set along with the architectural developments, which imparted substantial programming flexibility and improvement over the 8-bit microprocessor.
Instruction and data formats :
Memory used in the Intel 8086 microprocessor is organized in 8-bit , i.e. It is byte organized .
Every byte has a unique location in physical memory .
The address bus of 8085 is 16-bit wide , so the location of memory is described by one of a sequence of 16-bit binary address .
The 8085 can address up to 64k(i.e. 65,535) bytes of memory , which may consist of both RAM and ROM .
Addressing Modes :
The 8085 has four different modes for addressing data stored in memory or in registers –
Direct : Bytes 2 and 3 of the instruction contains the exact memory address of the data item( the low-order bits of the address are in byte 2 , the high-order bits in byte 3 )
Register : The instruction specifies the register or register pair in which the data are located .
Register Indirect : The instruction specifies a register pair which contains the memory address where the data are located .( the high-order bits of the address are in the first register of the pair and the low order bits in the second ).
Immediate : The instruction contains the data itself . This is either and 8-bit quantify or a 16-bit quantify (least significant byte first , most significant byte second ).
Unless directed by and interrupt or branch instruction the execution of instructions proceeds through consecutively increasing memory locations.
A branch instruction can specify the address of the next instruction to be executed in one of two ways -
Direct: The branch instruction contains the address of the next instruction to be executed .
Regular Indirect : The branch instruction indicates a regular pair which contains the address of the next instruction to be executed .