Microcontroller Articles - Page 20 of 38

In this program we will see how to find the factorial of a number.Problem StatementWrite 8085 Assembly language program to find the factorial of an 8-bit number.DiscussionIn 8085, there is no direct instruction to perform multiplication. We need to perform repetitive addition to get the result of the multiplication. In each step we are decreasing the value of B and multiply with the previous value of B. We are repeating these steps until B reaches 1. and B – 1 to 0. Thus the factorial is generated.InputAddressData800005Flow Diagram ProgramAddressHEX CodesLabelsMnemonicsCommentsF00021, 00, 80 LXI H, 8000HLoad the numberF00346 MOV B, MTake number from memory ... Read More

In this program we will see how to multiply using logical operators.Problem StatementWrite 8085 Assembly language program to multiply two 8-bit numbers using logical operators.DiscussionWe are assuming the first number is in register B, and second number is in register C, and the result must not have any carry.Here we are multiplying with 04H. We can perform the multiplication by left rotate two times. Assign 06H into B, and 04H into C. Load B to A, then rotate the accumulator two times. Store the result into a specified memory.InputRegisterDataB06C04Flow Diagram ProgramAddressHEX CodesLabelsMnemonicsCommentsF00006, 06 MVI B, 06H F0020E, 04 MVI C, 04H F00478 MOV A, BLoad B ... Read More

In this program we will see how to add three 16-bit numbers stored in register pairs.Problem StatementWrite 8085 Assembly language program to add three 16-bit numbers stored in register pair BC, DE and HL. Store the result at DE register pair.DiscussionIn this program we are storing the 16-bit numbers into BC, DE and HL pair. We have DAD D instruction which helps to add HL and DE register pair, and store the result into HL pair. After that copy BC to DE, then again perform DAD D to add them. Finally using XCHG we are storing them into DE register ... Read More

The select unit of the register in the 8085 selects any one of the register pairs (BC, DE, HL, SP, PC, or WZ) for sending them to it to the latch unit specified for addressing. For example, the contents of the PC be C200H. If the selection unit be the register which selects the PC, and sends C200H from the PC to the address latch internally thereafter the latch holds the specified value and sends directly out to the pins of the address after buffering. The Most Significant Byte of the address i.e. the C2H, is sent out to the ... Read More

Address and data buffers are used for bidirectional data transfer. They perform the unidirectional data transfer when they send out the Least Significant Byte of the address. These buffers are only used for increasing the driving capacity of the current. Through the internal bus data goes to the buffers. The Least Significant Byte of the address goes to the buffers from the internal address latch to the other.Hence the address or data are sent out on the address ranging from AD7 to AD0 can drive every external chips, like chips of RAM, chips of EPROM, and other peripheral chips meant for ... Read More

Let us consider the instruction to be executed as “MOV A, C”. Here in this case the value of 8 bit in the register C must be moved to the register. The given set of registers namely B, C, D, E, H, and L must be connected to the internal bus by means of a multiplexer (many input but only one output) or demultiplexer the reverse of multiplexer. The register meant to carry the work selects the specific unit and sends the appropriate code to the multiplexer such that the contents of register C are sent out to the multiplexer ... Read More

Temporary register is also an 8-bit register which the programmer can’t access at all. It is temporarily stored inside 8085 microprocessor which is 8 bit operand to the instruction set. For example, when the fetching of instructions “MVI M, 34H” is done the instruction register IR register will receive the opcode for MVI M, and the Temp register receives 34H.The operations of arithmetic and logical sequence carried out involves two operands, among which one is operand is provided by the accumulator, and the other operand is provided by the Temp register. For example, in the addition process the instruction to ... Read More

We use Timing and Controlling unit in 8085 for the generation of timing signals and the signals to control. All the operations and functions both interior and exterior of a microprocessor are controlled by this unit. X2 and CLK output pins: To do or rather perform the operations of timing in the microcomputer system, we have a generator called clock generator in the CU of 8085. Other than the quartz crystal the complete circuit of the oscillator is within the chip. The two pins namely X1 and X2 are taken out from the chip to give the connection to the ... Read More

The main differences between a JMP instruction and a CALL instruction is as follows –If a JMP instruction is executed, we jump to the destination location, and the execution carries on from there, without bothering to come back later to the instruction after the JMP. On the other hand, if a CALL instruction is executed, we jump to the subroutine, and the execution carries on from there till the RET instruction is executed in the subroutine, and then we come back to the instruction after the CALL in the main program.The address of the next instruction after the CALL instruction ... Read More

To define Temporary Register, we can mention that it is an 8-bit non-programmable resister used to hold data during an arithmetic and logic operation (temporary resister is used to hold intermediate result). The result is stored in the accumulator, and the flags (flip-flops) are set or reset according to the result of the operation.W and Z are two 8-bit temporary registers of 8085 microprocessor, which is not accessible to the user. They are exclusively used for the internal operation by the microprocessor. These registers are used either to store 8-bit of information in each W and Z registers or a ... Read More