A physical device capable of storing energy in the form of the electric field in the dielectric medium when voltage is applied across it.
In the following video, you will find explanations to:
To calculate the value of a resistor from colour codes.
Then, First, you have to locate the Tolerance band.
The tolerance band mostly in most of the resistors is made from either gold colour or silver colour.
Then you need to look at the next band which tells you the multiplier.
Then you need to look at the opposite end of the resistor and note down the colour in order till the multiplier.
The first band from the left gives us the first digit.
The next band gives the next digit.
A resistor is an electronic component that offers resistance in the flow of current. The practical resistor has a slight shift in its values from the ideal counterparts.
Not all the values of the resistor are available in the market. There is a certain number that is chosen and is readily available. If a particular value is to be achieved then a combination made from the selected resistors is to be used.
An ideal resistor follows Ohm’s law.
A practical resistor changes its value if the surrounding temperature, pressure and changes in mechanical dimension etc. Though there are very nominal changes yet they differentiate the ideal resistor from the practical counterpart.
The resistors value is generally marked on the surface. If the resistor is big, standard values along with manufacturing company seal are also printed on top of it.
For very small resistors; either colour bands or some code is written on top of it. As the size goes on decreasing the surface area becomes small and reaches a point where it is not feasible to print anything that can be visible to the naked eye. Then the values are written beside the component.
There are two types of resistors.
It is important to consider the power dissipation of a resistor. Since resistor obstructs the flow of current. The obstruction causes a buildup of energy which needs to dissipate. If this energy is not released then it will burn the resistor or permanently change its resistance values. So resistors use heat to dissipate the energy.
for example:
Let’s consider an 8-ohm resistor that resists the flow of current.
A voltage source of 9V has connected across. The 8-ohm resistor drops the voltage from 8V to 0V. Blocking a significant portion of voltage that is 8V.
and Let’s say the current flowing in the circuit is one Ampere.
So the resistor needs to dissipate 8W of energy.
Now you need to select a resistor that can dissipate more than 8W of energy. and the next best option is to use a resistor of 10 watts.
It uses ARM v7E-M architecture.
It a Harvard based architecture with two distinct buses for data and memory.
It has all the instruction set of M0, M1 and M3 .
It also has an additional feature set to support Floating-point Arithmetic. IEEE754 standard in single precision and double precision.
The following points are from the programming model.
There are three modes of operations:
Two thread mode are given to support a operating system. Kernel software run in priviledged mode and the user application software runs in unprivledged mode.
Unprivileged mode has some restriction on memory access.
Privileged mode has full access to system resources.
If an operating system is running and a user application needs to access the Privileged resources it has to generate an exception/interrupt and then the interrupt will be taken by the handler and put the system in privilege mode.
You can switch from privilege mode to unprivileged mode by setting nPRIV and SPSEL bit in the CONTROL register.
Just like all the other processors ARM Cotex M4 has registers and pointer registers.
The major difference is the use of two different stack pointer registers.
If application is running in privileged mode than main stack pointer will be used. And if the application is working in unprivileged the process stack pointer will be used.
General Purpose Registers:
R0 – R12 – General Purpose Register
R13 – Stack Pointer (SP) {MSP and PSP}
R14 – Link Register (LR)
R15 – program counter (PC)
Special registers:
There are 32 FPU registers from s0 to s31.
They group together to form a single 64-bit register. which are from D0 to D15
There is a Floating Point Status and Control Register (FPSCR).
There are lot of ARM based microcontroller offered by ST.
They use ARM Cortex M processor with ST peripheral such as GPIO, ADC etc.
They mostly fall into these following groups:
Then there is ST classification :
The widely available stm32f1 microcontroller also known as the blue pill has ARM cortex M3.
STM32L4 has an ARM Cortex M4F.