Here we will see the data memory structures of 8051 microcontroller. The internal data memory of 8051 is divided into two groups. These are a set of eight registers, and a scratch pad memory. These eight registers are R0 to R7. The address range 00H to 07H is used to access the registers, and the rest are scratch pad memory.8051 Provides four register bank, but only one register bank can be used at any point of time. To select the register bank, two bits of PSW (Program Status Word) are used.So the following addressing can be used to select register ... Read More

Here we will see the address registers of 8257 chip.Every DMA channel consists an address register and a count register. These registers are 16-bits wide in length. In each 16 bits there are four ARs marked as AR3-0. Apart from four CRs there are control and status registers also. They are separate 8-bit registers, but have the same address. Here the processor can only write in the control register but we can read in the status register.We can select any one of the above registers by the address of the four pins marked as A3-0 of 8257. The processor used here ... Read More

In this section we will see how external RAM memories can be addressed by the Intel 8051 microcontroller. There are different methods for addressing the RAMs. Now at first we will discuss about some different types of RAM memories in short.The RAM (Random Access Memory) is volatile memory. So when the power is cutting off to the RAM chip, it losses the data. RAMs are also known as RAWM (Read and Write Memory). There are basically three kinds of RAMs. These are SRAM (Static RAM), NV-RAM (Non-Volatile RAM) and DRAM (Dynamic RAM).Static RAMThe storage cell in Static RAM are made ... Read More

Here we will see the division operation. This operation will be used to divide two 8-bit numbers using this 8051 microcontroller. The register A and B will be used in this operation. No other registers can be used for division. The result of the division has two parts. The quotient part and the remainder part. Register A will hold Quotient, and register B will hold Remainder.We are taking two number 0EH and 03H at location 20H and 21H, After dividing the result will be stored at location 30H and 31H.AddressValue …20H0EH21H03H …30H00H31H00H …Program      MOV R0, #20H ; set source address 20H ... Read More

Here we will see how to multiply two 8-bit numbers using this 8051 microcontroller. The register A and B will be used for multiplication. No other registers can be used for multiplication. The result of the multiplication may exceed the 8-bit size. So the higher order byte is stored at register B, and lower order byte will be in the Accumulator A after multiplication.We are taking two number FFH and FFH at location 20H and 21H, After multiplying the result will be stored at location 30H and 31H.AddressValue …20HFFH21HFFH …30H00H31H00H …Program      MOV R0, #20H ; set source address 20H to R0 ... Read More

Now, in this section we will see how to subtract two 8-bit numbers using 8051 microcontroller. The register A (Accumulator) is used as one operand in the operations. There are seven registers R0 – R7 in different register banks. We can use any of them as second operand.We are taking two number 73H and BDH at location 20H and 21H, After subtracting the result will be stored at location 30H and 31H.AddressValue …20H73H21HBDH …30H00H31H00H …Program      MOV R0, #20H ; set source address 20H to R0       MOV R1, #30H ; set destination address 30H to R1       ... Read More

Here we will see 8085 program. This program will divide two 8-bit numbers using 8085 microprocessor.Problem Statement −Write an 8085 Assembly language program to divide two 8-bit numbers and store the result at locations 8020H and 8021H.Discussion −The 8085 has no division operation. To get the result of division, we should use the repetitive subtraction method.By using this program, we will get the quotient and the remainder. 8020H will hold the quotient, and 8021H will hold remainder.We are saving the data at location 8000H and 8001H. The result is storing at location 8050H and 8051H.InputThe Dividend: 0EHThe Divisor 04HThe Quotient will be ... Read More

Here we will see one 8085 program. In this program we will see how to subtract two 8-bit numbers.Problem Statement −Write an 8085 Assembly language program to subtract two 8-bit numbers and store the result at locations 8050H and 8051H.Discussion −In 8085, the SUB instruction is used 2’s complemented method for subtraction. When the first operand is larger, the result will be positive. It will not enable the carry flag after completing the subtraction. When the result is negative, then the result will be in 2’s complemented form and carry flag will be enabled.We are using two numbers at location 8000H and ... Read More

Here we will see one 8085 assembly language program. In this program we will see how to add two 8-bit numbers.Problem Statement −Write an 8085 Assembly language program to add two 8-bit numbers and store the result at locations 8050H and 8051H.Discussion −To perform this task, we are using the ADD operation of 8085 Microprocessor. When the result of addition is 1-byte result, then the carry flag will not be enabled. When the result is exceeding the 1-byte range, then the carry flag will be 1We are using two numbers at location 8000H and 8001H. When the numbers are 6CH and 24H, ... Read More

In this section we will see one Intel 8085 Microprocessor program. This program is mainly for adding multi byte numbers.Problem Statement −Write an 8085 Assembly language program to add two multi-byte numbers.Discussion −We are using 4-byte numbers. The numbers are stored into the memory at location 8501H and 8505H. 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 byte count. We are using ... Read More