Microprocessors
are generally comprised of: ALU (Arithmetic Logic Unit), Control and Timing
Unit, and Array Register (Register Array). The block diagram shown in Figure
1.4. Microprocessor main function is as a unit that controls the entire working
microprocessor system.
Microprocessor consists
of several parts:
1. Register,
serves as a temporary storage area for data, address, status bits of code and
operating a variety of microprocessors. Function is similar to a microprocessor
memory device with the difference that: the memory is outside the
microprocessor while the register is inside the microprocessor. Memory is
identified by the address while the register is identified by the name of the
register by the microprocessor.
2. ALU
(arithmetic and logic unit), serves to do the commands of logic and arithmetic
operations to process the data.
3. Timing
and Control Unit, used to retrieve and decode instructions from program memory
and generate control signals needed by other parts of the microprocessor to
carry out those instructions. Timing and Control Unit serves as a generator
cycle-time to interface with peripherals on the bus address, data and control.
Additionally control buses and other additives such as interrupts, DMA and
others.
4. The
memory used to store data that is used both as a program and as a store of data
processed by the CPU. Two types of memory that is known is the RAM (Random
Access Memory) and ROM (Read Only Memory). Both types of memory when used in
microprocessor-based systems are generally placed on accessing different
spaces. This can be done by creating a memory map for both types of this
memory.
Based
on whether or not the missing data / programs in storage, namely:
a) Volatile
Storage, data or program files will be lost if the power goes out.
b) Non-Volatile Storage. Data file or program
will not be lost even if electricity turned off.
By Accessing memory is
divided into two, namely:
·
RAM (RANDOM ACCESS MEMORY). Part of the
main memory, which we can enter data or program from diskette or other sources.
Where the data can be written or read on location anywhere in the memory. RAM
is volatile
·
ROM (READ ONLY MEMORY). Read-only
memory. Charging ROM with programs and data, is done by the factory. ROM is
usually already written program or data from the factory with specific goals.
Eg: Filled translators (interpreters) in basic language. So ROM does not
include a memory that we can use for the programs we make. ROM is non volatile
Other types of ROM
chips, namely:
·
PROM (Programmable Read Only Memory)
is
a memory chip that can only be filled in with data only once. Once the program
was put into a PROM, then the program will be on the next PROM. Unlike RAM, the
PROM data will still exist even if the computer is turned off.
The
fundamental difference between a PROM and a ROM (Read Only Memory) is that PROM
manufactured as blank memory, whereas the ROM has been programmed at the time
produced. To write data on a PROM chip, it takes 'PROM Programmer' or 'PROM
Burner'
·
EPROM (Erasable Programmable Read Only
Memory).
A
special type of PROM that can be removed with the aid of ultraviolet light.
Once removed, EPROM can be programmed again.
·
EEPROM (Electrically Erasable
Programmable Read Only Memory).
EEPROM
is similar to EPROM, only to erase data requires an electric current.
EEPROM
is a special type of PROM (Programmable Read-Only Memory) that can be removed
by using an electrical charge. As with other types of PROM, EEPROM can store
the contents of the data, even when the power is turned off.
Operating system memory work,
principally consists of two operations, namely read and write operations. When
the processor perform memory read command to the processor sends the address
data to be accessed, then sends control signals read (read) ordered in memory
to issue the data at the address indicated on the data bus. The write operation
is when the processor will store data, information, instruction or operation
code into memory. In a data write operation, the microprocessor first sends the
address via the address bus to the memory, which indicates the location of the
data on the memory address to be written. The next signal write (write) is sent
giving orders to memory to make room in memory for existing data on the data
bus with the address as shown on the address bus. Memory work cycle is shown in
the following figure.
Explanation Figure 1.5
are as follows:
·
Microprocessor put the address data to
be read on the address bus.
·
Microprocessor control gives a pulse
signal read (active low).
·
When the control signal is active low,
the data on the data bus is ready for collection / read.
·
valid data ready for reading by the
microprocessor
·
The processor retrieves data from the
data bus
·
Control signals back to a high level.
Figure1.6. Diagram cycle time write operation on memory
Explanation of Figure
1.6 are as follows:
·
Microprocessor provide data to be
written to the memory on the data bus.
·
The microprocessor further provides data
on the location of the memory address for the data to be written to the memory
address bus.
·
The processor then give write control
signal (active low).
·
When the control signal is at a low
position, the data is automatically written to the memory address of the
location at the address shown in the address bus.
·
Control signals back to a high level.
·
Memory is ready to receive further
instructions.
5. Unit Input and Output
Intermediary between the microprocessor and the
outside world is the duty of the input unit and output to a system
microprocessor. Without the input and output unit, the data is processed just
spinning in microprocessor systems, without any environmentally acceptable
output outside the system microprocessor.
Engineering
input and output in microprocessor systems can be divided into two systems,
namely:
·
Parallel Systems, Data input / output is
sent in the form of eight-bit parallel.
·
Serial System, Data input / output is
sent bit by bit sequentially through one lane.
Some other functions of
microprocessors, among others:
1. Taking
instructions and data from memory.
2. Transferring
data to and from memory.
3. Sending
control signals and serves an interrupt signal.
4. Provide
a cycle timing for microprocessor systems.
5. Working
functions - the functions of logic and arithmetic operations.
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