Carry, Half Carry, and Zero flag in AVR Atmega32 using Atmel Studio

Here we are writing a program of Carry, Half Carry, and Zero flag in AVR Atmega32 using Atmel Studio an Atmega microcontroller in which we see how to add values and it affects the status register. But before moving forward you need to know what the status register is.

The status register is a flag register. The PIC flag register is typically an 8-bit register. It is additionally known as a status registry. The PIC18 uses just 5 of the status register’s 8 bits, despite its size. The three unutilized bits are read as 0, as they are not used. The five flags are referred to as conditional flags since they inform us of certain situations that may arise from the execution of the instructions. These five flags stand for carry (C), digital carry (DC), zero (Z), overflow (OV), and negative (N).

The bits of the status register are shown in the picture below. A conditional branch jump can be executed using any of the conditional flags.

Status Register

The representation of the 8 bits in the status register are:

• Bit 0: Carry Flag
• Bit 1: Zero Flag
• Bit 2: Negative Flag
• Bit 3: Two’s Complement Overflow Flag
• Bit 4: Sign Bit
• Bit 5: Half Carry Flag
• Bit 6: Bit Copy Storage
• Bit 7: Global Interrupt Enable

Let us understand it through a program in assembly language.

Firstly, we will include a header file.

CODE OF Carry, Half Carry, and Zero flag:

.INCLUDE “M32DEF.INC”

If you do not know how to include it, you can check by clicking here.

To get to know about the labels let’s start by writing a mini instruction.

First of all, we will add some values for this you need to load these values in general-purpose registers.

LDI R16, 0X92         //R16=92

LDI R17, 0X23

LDI R18, 0X66

LDI R19, 0X87

LDI R20, 0XF5       //R20=F5

Here the X represents that this is a hex value.

Now after loading the values, we will add these values like adding the value of R16 into the R17. Then R16 will have the value of both the sums as shown below.  Because R16 is the destination register.

ADD R16, R17       //R16=R16+R17

ADD R16, R18

ADD R16, R19

ADD R16, R20      //R16=R16+20

Now we will run our code by pressing F7 or you can find this option from the menu bar.

DEBUG:

Now we will further check the backend simulations of our program from the debug option in the menu bar.

As you can see above the 92 values have been loaded in the R16 register.

By further moving to the next step, the value 23 has been loaded in register 17.  Similarly, we will see all the values have been loaded in their respective registers as shown below.

Now we will check our status registers to verify the addition operation.

As you can see, the value in the R16 has been updated after adding the value of R16 and R17.

So, the next step is to check the status register, as it is an 8-bit register. After adding the 2 values, the status register raised its 2 flags sign bit and a negative flag. A negative flag means the value is the complement of the original value.

Here we can see that when we further proceed with the process i.e.,  when R18 is added in the R16, the Carry flag is raised.

Here when we added R19 to R16, three flags were raised which are the sign flag, negative flag, and half carry flag.

Now the status register raised 3 flags that are sign bit, negative flag, and carry flag. Here the red color changed to blue which means that these flags had already been raised for the previous values now they are again raised.

Conclusion

In conclusion, Carry, Half Carry, and Zero flags in AVR Atmega32, when we’re working with Atmel Studio, are like special indicators that help the microcontroller understand what’s happening during its tasks. The Carry flag is like a signal that says if something went too big or too small in a calculation. The Half Carry flag helps with certain math problems, and the Zero flag checks if the result is equal to zero.

These flags are useful tools for making sure the microcontroller does its job correctly and safely, especially when working on complex projects with Atmel Studio. Understanding these flags can make it easier to create successful programs for the AVR Atmega32 microcontroller.

For Complete Trial Watch the Video: Carry, Half Carry, and Zero flag in AVR Atmega32 using Atmel Studio

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