In this section, we will see the basic architecture of the Motorola M6800 Microprocessor, and different registers to write programs into it.To write programs we have to care about the registers and some instructions to access them during program execution. So from this diagram, we can see that there are two ... Read More

The Intel 8085 is an 8-bit microprocessor produced by Intel and introduced in 1976. It is a software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added interrupt and serial input/output features. When the 8085desires to receive 8-bit information, it receives it on ... Read More

This is one of the methods of representing signed integers in the computer. In this method, the most significant digit (MSD) takes on extra meaning.If the MSD is a 0, we can evaluate the number just as we would any normal unsigned integer.If the MSD is a 1, this indicates that ... Read More

Now let us see the internal registers, memory and other details from the Programmer’s point of view.There are these componentsEight registers(8-bit) R0 to R7Register A and B.These are also 8-bit registersPSW, Stack Pointer(SP), four ports (P0 to P3). These are also 8-bitDPTR register of 16-bit. This is divided into two ... Read More

In 8051 Microcontroller there are 24 different instructions under the Arithmetic Group. In total there are 64 opcodes. The Carry Flag (CY), Auxiliary Carry (AC)and Overflow flag (OV) are affected based on the result of ADD, ADDC, SUBB  etc. instructions. The multiple and divide instructions clear the Carry flag, and ... Read More

Unsigned binary integers are numbers without any ‘+’or ‘-’ sign. Here all bits representing the number will represent the magnitude part of the number only. No bits will remain reserved for sign bit representation. An unsigned binary integer is a fixed-point system with no fractional digits.Some real life Examples are ... Read More

Here we will see a problem to shift some multi-byte BCD number to the right. The BCD numbers are shifted by two digits (8-bit). Let us consider a four-byte BCD number (45 86 02 78) is stored at location 20H, 21H, 22H, 23H. The address 10H holds the number of bytes ... Read More

In this section, we will see some bit manipulation operation using 8051. The 8051 supports some operations on different bits of an 8-bit number. The operations are like complementing, setting to 1, moving, ANDing, ORing etc.In this example, we are taking a number AEH from location 10H, then after performing ... Read More

Now we will try 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 ... Read More

In 8085 Instruction set, SIM stands for “SetInterrupt Mask”. It is 1-Byte instruction and it is a multi-purpose instruction. The main uses of SIM instruction are –Masking/unmasking of RST7.5, RST6.5, and RST5.5Reset to 0 RST7.5 flip-flopPerform serial output of dataMnemonics, OperandOpcode(in HEX)BytesSIM301When SIM instruction is executed then the content of ... Read More