Every time we use our computer equipment we make use of memory, but in reality we do not realize how it is that each instruction, operation or movement that we carry out is registered in memory, ready at all times to be used again.
In this document we will try to dispel that doubt and in the same way have the knowledge of how communication occurs internally in a computer.
DEVELOPING
Main memory is a set or collection of small cells that store information (data and instructions) that are uniquely identified by an address.
To access a specific address, the CPU sends signals on the address bus, which is approximately 32 bits in size, and these allow us to specify 4,296,967,296 (232) different memory addresses to the CPU.
To begin, we will make it clear that the representation of memory locations is represented by the hexadecimal number system; The rationale for this is because of the following.
Speaking of an 8-bit address bus, it has access to 256 positions (Range 00-FFh).
On the address bus that has 20 bits, the possibilities are 1,048,576 (Range 00000-FFFFFh).
If we deal with 16-bit addresses, we have access to 65,536 positions (Range 0000-FFFFh).
The functioning of memory is similar to the method used to order correspondence in a post office. Each data bit is assigned an address and each address corresponds to a location in memory.
The process for storing the information in memory occurs as follows:
The processor sends the address for the data.
The memory controller finds the appropriate location.
Finally, the processor sends the data to write.
Reading the information goes through a similar process:
The processor sends the address of the requested data.
The memory controller finds the information bits contained in that address.
It then sends them to the processor's data bus.
1 TYPES OF MEMORY ASSIGNMENT
The memory allocation to each new record can be considered from 2 points, which are the following: Physical and Logical.
Within the Physicist we can access the different memory positions through electronic means.
Within the logical medium we will find how the addresses are expressed and stored.
1.1 LOGICAL ALLOCATION OF MEMORY
If we talk about logical allocation we will find that the following exist:
- Dynamic allocation Static allocation
For example, when we work in a programming language we require memory allocation and it is done in the following way, where it usually begins with some of the following literals that are part of memory: CS, SS, DS and IT IS
Within the Physicist we can access the different memory positions through electronic means.
The records can be classified into 2 types:
Operational circuit: capable of accumulating binary information on its flip-flops and has gates capable of performing data processing tasks.
Storage register: used only for the temporary storage of binary information, which cannot be altered when transferred either into or out of the register.
Where a memory unit is a collection of storage registers together with the associated circuits necessary for the transfer of information, which are called memory registers; This stores the information in groups called words and each of them is stored in a memory register.
The information transferred to the output elements is taken from the registers in the memory unit, sent to the operational registers, and the result of this is returned to the memory registers.
1.2.1 Basic properties of the component that makes up the binary cells in the memory unit
- Two-state dependent property for binary representation. Being small in size. Low cost per bit of storage. Effective access time.
For example: Magnetic cores, semiconductor ICs, and magnetic surfaces of tapes, drums, and disks.
A word is an x-bit entity that moves in and out of storage as a unit, it can represent an operand, an instruction, or a group of alphanumeric characters or any binary coded information.
Communication between a memory unit and its surroundings is accomplished by two signals:
The control signals: specify the direction of the required transfer, when a word must be accumulated in a memory register or when a previously stored word must be transferred out of the memory register.
External registers: One specifies the memory register chosen from the thousands available; another specifies the bit configuration of that word.
The memory address register specifies the selected memory word. Each one is assigned an identification number starting from 0 to the maximum number of words available, then the location or address number is transferred to the address register.
The two control signals applied to the memory unit are called read and write, each is referenced by the memory unit.
The internal memory circuits accept this address from the register and open the necessary paths to select the word.
After accepting one of the signals, the internal control circuits within the memory unit supply the desired function. The primary information is destroyed when the new information is written. The sequence of internal control in a destructible read memory must provide control signals that can cause the word to be restored in its binary cells.
Information transferred into and out of registers in memory and to the external environment is communicated through a register called a memory buffer register. When the memory unit receives a write control signal, the internal control interprets the contents of the separator register as the bit setting of the word to be stored in a memory register. With a read control signal, the internal control sends the word from the memory register to the separator register.
The sequence of operations necessary to communicate with the memory unit to transfer an outward word to the BR is:
- Transfer address bits of selected word to AR. Activate read control input.
The sequence of operations necessary to store a new
- Transfer the address bits of the selected word to the MAR. Transfer the data bits of the word to the MBR. Activate the write control input.
Memory unit properties:
Built with semiconductor ICs, they retain the information in the memory register during the reading process so that no loss occurs.
Magnetic core, loses the binary information stored during the reading process, due to this it must have additional control functions to reset the word to the memory register.
Addressing methods
Generally an instruction consists of an operation part and a direction part.
The address part contains the address of an operand used in executing the instruction or the address where the address of the operand is located; the first case the direction is direct direction, the second is indirect operation.
- DIRECT. The instruction contains the address of the memory location where the operand is located. INDIRECT. Contains the address where the address of the operand is located. It contains the number N. In memory the address of the operand is found by adding the number N to the number of the program counter. INDEXED. Contains a number N that can be positive or negative IMMEDIATE. Contains the same operand, among others
Access modes
The access mode of a memory system is determined by the type of components used.
- Random access memory, records are separated in space, with each record occupying a particular spatial place in a memory of magnetic cores. Sequential access memory, information stored on some medium is not immediately accessible but is obtained only at certain intervals of time.
CONCLUSION
Addressing not only consists of performing it at a logical level, in order to achieve it, the type of hardware that the machine has is very important and the speed with which said operation can be carried out depends on it.
Memory allocation is considered from several perspectives where one of them is static allocation which refers to the process of allocating memory at compile time before the associated program is executed, and on the other hand we find the dynamic allocation or the automatic where memory is allocated when required at runtime.
In this way you can have a clearer and more precise idea of how memory allocation is carried out, which is a rather interesting deep topic.
BIBLIOGRAPHY
www.monografias.com/trabajos/memoria/memoria.shtml
es.wikipedia.org/wiki/Asignaci%C3%B3n_de_memoria#Asignaci.C3.B3n_din.C3.A1mica_de_memoria
es.wikipedia.org/wiki/Asignaci%C3%B3n_de_memoria
es.wikipedia.org/wiki/Direcci%C3%B3n_de_memoria
www.zator.com/Hardware/H5_1.htm
