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Often, you may have a lot of print statements in your Arduino code. These are generally stored in the SRAM.However, if your sketch has too many of these print statements, they can fill up the SRAM very quickly. In such a scenario, it may be wise to store these print statements within flash memory (flash memory is generally much larger in size than SRAM). This is assuming that your sketch doesn't occupy the entire flash memory (which it generally doesn't).ExampleA print statement like −Serial.print("A typical constant string to be printed");Can be replaced with the following −Serial.print(F("A typical constant string to ... Read More
PROGMEM is the keyword you use when you wish to store data in the program memory (flash) instead of the SRAM. While you can use PROGMEM for a single variable, it won't make much sense to do so. After all, the SRAM would have more than enough space to accommodate your single variable, and it will be faster to access the variable stored in SRAM.PROGMEM is primarily used for large chunks of data (an array mostly), which can overwhelm the SRAM (which is generally much smaller in size than the flash memory, but faster to access). The implication of storing ... Read More
CRC stands for Cyclic Redundancy Check (CRC). It is, in simple words, an algorithm used to detect errors in received messages. The idea is similar to parity, but this is much more robust.If a transmitter is sending a packet to a receiver, the transmitter will calculate a CRC code based on some polynomial calculations on the packet, and append it to the packet. The receiver will perform the same calculations on the packet, and check if the generated CRC matches the CRC that came in with the packet. If the two match, there were no errors introduced in the transmission, ... Read More
AVR libraries are developed by Atmel. You might be knowing that the microcontrollers used in most Arduino boards are Atmel microcontrollers (ATmega328P, ATmega2560, etc.). AVR libraries for several specific operations (sleep, time, etc.) already exist, and therefore, we may greatly benefit if we are able to import AVR libraries within Arduino. The good news is that we can!As per Arduino's website, "AVR libraries have the potential to greatly extend the Arduino language. The Arduino system is based on the avr-gcc compiler and makes use of the standard AVR libc libraries, which are open-source C libraries, specifically written for Atmel hardware, ... Read More
A watchdog timer is an essential part of any microcontroller. It resets the program if the program gets stuck anywhere. Very briefly, this is how the watchdog timer works −The timer keeps incrementing.The program has to ensure that it keeps resetting the timer, i.e. does not allow it to overflow.If the timer overflows, it means that the program was stuck somewhere and therefore was unable to reset the timer. An interrupt is generated on timer overflow which resets the microcontroller.To implement watchdog timer in Arduino, we use the avr wdt library.The code is given below −#include void setup() { ... Read More
The microinstructions can be determined by symbols. It is interpreted to its binary format with an assembler. The symbols should be represented for each field in the microinstruction. The users should be enabled to represent their symbolic addresses. Each line in an assembly language represents symbolic instruction. These instructions are divided into five fields such as label, micro-operations, CD, BR, and AD.The fields that specify the following information are as follows −The label field may be empty or it may specify a symbolic address. A label is terminated with a colon (:).The micro-operations field consists of one, two, or three ... Read More
A microinstruction format includes 20 bits in total. They are divided into four elements as displayed in the figure.F1, F2, F3 are the micro-operation fields. They determine micro-operations for the computer.CD is the condition for branching. They choose the status bit conditions.BR is the branch field. It determines the type of branch.AD is the address field. It includes the address field whose length is 7 bits.The micro-operations are divided into three fields of three bits each. These three bits can define seven different micro-operations. In total there are 21 operations as displayed in the table.Symbols with their Binary Code for ... Read More
The microcode for the control memory should be generated by the inventor once the configuration of the computer is settled. The generation of code is known as microprogramming.There are various points to be treated while designing the microprogram sequencer are −Size of the microinstructionTime of address generationThe microinstruction’s size should be in the least, therefore that the control memory necessary is less and the cost is decreased. Microinstructions can be implemented at a quicker rate if the time to create an address is less. This results in raised throughput.Disadvantage of Micro-program SequencingThe disadvantage of microprogram sequencing is as follows −If ... Read More
Subroutines are programs that are used by other routines to accomplish a particular task. A subroutine can be called from any point within the main body of the micro-program. Frequently, many micro-programs contain identical sections of code. Microinstructions can be saved by employing subroutines that use common sections of microcode.For example, the sequence of micro-operations needed to generate the effective address of the operand for instruction is common to all memory reference instructions. This sequence could be a subroutine that is called from within many other routines to execute the effective address computation.Micro-programs that use subroutines must have a provision ... Read More
A unique type of branch exists when a microinstruction defines a branch to the first word in control memory where a micro-program routine for instruction is placed. The status bits for this type of branch are the bits in the operation code part of the instruction. For example, a computer with a simple instruction format as shown in the figure.It has an operation code of four bits which can specify up to 16 distinct instructions. It can consider that the control memory has 128 words, needing an address of seven bits. For each operation code, there exists a micro-program routine ... Read More