Microcontroller Articles - Page 29 of 33

Using 16-bit address, 8085 can access one of the 216= 64K locations. As a single hexadecimal digit can be expressed in4-bit notation so, in 8085, memory address can be expressed using four hexadecimal digits. Similarly, for convenience, we can represent all 8085 CPU registers as A, B, C etc. using binary notations. Internally 8085 specifies these registers using 0s and 1s only. So3-bits are just enough to represent a register. The 3-bit register codes for the registers of 8085 are shown in the following tableWith 3-bit register code, eight registers can be specified in maximum as 23= 8. On the ... Read More

In this program, we will see how to multiply two 8-bit numbers using 8085 microprocessor.Problem StatementWrite 8085 Assembly language program to multiply two 8-bit numbers stored in a memory location and store the 16-bit results into the memory.DiscussionThe 8085 has no multiplication operation. To get the result of multiplication, we should use the repetitive addition method. After multiplying two 8-bit numbers it may generate 1-byte or 2-byte numbers, so we are using two registers to hold the result.We are saving the data at location 8000H and 8001H. The result is storing at location 8050H and 8051H.InputAddressData......8000DC8001AC......Flow DiagramProgramAddressHEX CodesLabelsMnemonicsCommentsF00021, 00, 80LXI H, ... Read More

In this program, we will see how to check the 4th bit of an 8-bit number.Problem StatementWrite 8085 Assembly language program to check whether the fourth bit of a byte is 0 or 1.When it is 0, store 00H at any specified location, and when it is 1, store FFH at the specified location.DiscussionWe are considering the 8-bit number, and storing 00H or FFH by checking the 4th bit on the number from left. The logic behind it is very simple. We are just performing bit-wise and operation on the given data with 08H. If the result is non-zero, then the 4th ... Read More

In this program, we will see how to add a block of data using the 8085 microprocessor.Problem StatementWrite 8085 Assembly language program to add N 1-byte numbers. The value of N is provided.DiscussionIn this problem, we are using location 8000H to hold the length of the block. The main block is stored from address 8010H. We are storing the result at location 9000H and 9001H. The 9000H holding the lower byte, and 9001H is holding the upper byte.Repeatedly we are taking the number from the memory, then adding it with the accumulator and increase the register E content when carry ... Read More

In this program, we will see how to move blocks of data from one place to another.Problem StatementWrite 8085 Assembly language program to move a data block. The blocks are assumed to be non-overlapping. The block size is given, the block is starting from X and we have to move it to the location Y.DiscussionThe non-overlapping block movement is relatively an easy task. Here the block is starting at position X, we have to move it to position Y. The location Y is far away from X. So Y > X + block size.In this program, the data are stored ... Read More

Now let us see a program of Intel 8085 Microprocessor. This program is mainly for adding multi-digit BCD (Binary Coded Decimal) numbers.Problem StatementWrite 8085 Assembly language program to add two multi-byte BCD (Binary Coded Decimal) numbers. DiscussionWe are using 4-byte BCD numbers. The numbers are stored into the memory at location 8501H and8505H. One additional information is stored at location 8500H. In this place, we are storing the byte count. The result is stored at location 85F0H.The HL pair is storing the address of first operand bytes, the DE is storing the address of second operand bytes. C is holding the ... Read More

Register A is an 8-bit register used in 8085 to perform arithmetic, logical, I/O & LOAD/STORE operations. Register A is quite often called as an Accumulator. An accumulator is a register for short-term, intermediate storage of arithmetic and logic data in a computer's CPU (Central Processing Unit).In an arithmetic operation involving two operands, one operand has tobe in this register. And the result of the arithmetic operation will be stored or accumulated in this register. Similarly, in a logical operation involving two operands, one operand has to be in the accumulator. Also, some other operations, like complementing and decimal adjustment, ... Read More

Intel 8085 receives 8-bit information on AD7-0 from memory or in-port which resides inside the microprocessor via“register”. A register is a group of flip-flops, where each flip-flop can store a bit of information. To store 8 bitsof information, the size of a register in 8085 has to be 8 bitsThe advantages of a register over a memory location is the contents of a register can be accessed much faster by the microprocessor, compared with the contents of a memory location.However, the disadvantages of a register over a memory location are as follows.If there are too many registers, they occupy a lot ... Read More

In Intel 8085 microprocessor I/O and memory operation are differentiated by IO/m` status signal.IO/M` stands for ‘input-output/memory`’. When IO/M` is logic 0, it means that the address sent out by the processor is for addressing a memory location. When IO/M` is logic 1, it means that the address sent out by the processor is for addressing an I/O port.Fig: Pin diagram of 8085Let us consider this following example and also the voltage level at IO/M* pin. If we consider instruction MVI E, ABH then it means that ABH will be moved or copied to the register E. And as a ... Read More

Intel 8085 is an 8-bit microprocessor which has 16 address line for 16-bit address of a memory location. 8 higher order address bits are transferred through 8 bit lines out of this 16 address line while remaining lower order 8 bits of the address are sent through another 8 lines multiplexed with the 8-bit data lines. ALE (Address Enable Latch) is the control signal which is nothing but a positive going pulse generated when a new operation is started by microprocessor. So when pulse goes high means ALE=1, it makes address bus enable and when ALE=0, means low pulse makes ... Read More