07-11-2012, 01:14 PM
Microprocessor Architecture
[attachment=38397]
The microprocessor can be programmed to perform functions on given data by writing specific instructions into its memory.
The microprocessor reads one instruction at a time, matches it with its instruction set, and performs the data manipulation specified.
The result is either stored back into memory or displayed on an output device.
The Address Bus
16 bits wide (A0 A1…A15)
Therefore, the 8085 can access locations with numbers from 0 to 65,536. Or, the 8085 can access a total of 64K addresses.
“Unidirectional”.
Information flows out of the microprocessor and into the memory or peripherals.
When the 8085 wants to access a peripheral or a memory location, it places the 16-bit address on the address bus and then sends the appropriate control signals.
Microprocessor Initiated Operations
These are operations that the microprocessor itself starts.
These are usually one of 4 operations:
Memory Read
Memory Write
I/O Read (Get data from an input device)
I/O write (Send data to an output device)
The Read Operation
To read the contents of a memory location, the following steps take place:
The microprocessor places the 16-bit address of the memory location on the address bus.
The microprocessor activates a control signal called “memory read” which enables the memory chip.
The memory decodes the address and identifies the right location.
The memory places the contents on the data bus.
The microprocessor reads the value of the data bus after a certain amount of time.
The Internal Architecture
The Stack pointer
The stack pointer is also a 16-bit register that is used to point into memory.
The memory this register points to is a special area called the stack.
The stack is an area of memory used to hold data that will be retreived soon.
The stack is usually accessed in a Last In First Out (LIFO) fashion.
Tri-State Buffers
An important circuit element that is used extensively in memory.
This buffer is a logic circuit that has three states:
Logic 0, logic1, and high impedance.
When this circuit is in high impedance mode it looks as if it is disconnected from the output completely.
[attachment=38397]
The microprocessor can be programmed to perform functions on given data by writing specific instructions into its memory.
The microprocessor reads one instruction at a time, matches it with its instruction set, and performs the data manipulation specified.
The result is either stored back into memory or displayed on an output device.
The Address Bus
16 bits wide (A0 A1…A15)
Therefore, the 8085 can access locations with numbers from 0 to 65,536. Or, the 8085 can access a total of 64K addresses.
“Unidirectional”.
Information flows out of the microprocessor and into the memory or peripherals.
When the 8085 wants to access a peripheral or a memory location, it places the 16-bit address on the address bus and then sends the appropriate control signals.
Microprocessor Initiated Operations
These are operations that the microprocessor itself starts.
These are usually one of 4 operations:
Memory Read
Memory Write
I/O Read (Get data from an input device)
I/O write (Send data to an output device)
The Read Operation
To read the contents of a memory location, the following steps take place:
The microprocessor places the 16-bit address of the memory location on the address bus.
The microprocessor activates a control signal called “memory read” which enables the memory chip.
The memory decodes the address and identifies the right location.
The memory places the contents on the data bus.
The microprocessor reads the value of the data bus after a certain amount of time.
The Internal Architecture
The Stack pointer
The stack pointer is also a 16-bit register that is used to point into memory.
The memory this register points to is a special area called the stack.
The stack is an area of memory used to hold data that will be retreived soon.
The stack is usually accessed in a Last In First Out (LIFO) fashion.
Tri-State Buffers
An important circuit element that is used extensively in memory.
This buffer is a logic circuit that has three states:
Logic 0, logic1, and high impedance.
When this circuit is in high impedance mode it looks as if it is disconnected from the output completely.