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Microprocessor Articles
Page 7 of 42
Accumulator or Register A in 8085 Microprocessor
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 MoreRegisters of 8085 Microprocessor
It has eight addressable 8-bit registers: A, B, C, D, E, H, L, F, and two 16-bit registers PC and SP. These registers can be classified as −General Purpose RegistersTemporary Registers: a) Temporary data register b) W and Z registersSpecial Purpose Registers: a)Accumulator b) Flag registers c) Instruction registerSixteen-bit Registers: a) ProgramCounter (PC) b) Stack Pointer (SP)General Purpose RegistersRegisters B, C, D, E, H, and L are general purpose registers in 8085 Microprocessor. All these GPRS are 8-bits wide. They are less important than the accumulator. They are used to store data temporarily during the execution of the program. For ...
Read MoreAD7-0 pins in 8085 Microprocessor
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 these eight pins AD7, AD6, …, AD0. These eight pins are collectively called AD7-0. They are called basically “Address Data”. When the 8085 desires to send out 8-bit information, it sends it out on these same pins. these pins are bi-directional pins.The same lines are used for both receiving information and ...
Read MoreProgram memory structure of Intel 8051
We have already discussed that the 8051 microcontroller has the internal program memory. In this chip, there is EA pin. It indicates the External Access. So by using this pin, we can check whether the internal program memory is used or not. So when there is a low signal in this pin, the internal 4K bytes of program memory is not used, but in this situation, it can access only the ROM.When we are trying to access the external data memory, then the read RD or write WR will be the output from 8051. So for reading the data from ...
Read MoreData Memory Structure of Intel 8051
The 8051 has 128 bytes of On-Chip RAM. So for accessing that RAM area, the address space is 00H to 7FH. When we need more data memory, we can use external RAM. The address space of external RAM is 0000H to FFFFH.The external and internal data memory can be added to increase the total amount of data memory. When we are trying to access the external data memory, then the read RD or write WR will be the output from 8051. The external data memory address can be either 8-bit or 16-bit wide. Generally, the one 8-bit address is used ...
Read More2's complement notation
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 the number is negative.The other bits indicate the magnitude (absolute value) of the number.If the number is negative, the other bits signify the 2'scomplement of the magnitude of the number.Thus a positive number has the same representation in SM, 1's complement, and 2's complement notations. Only negative numbers are represented ...
Read MoreProgrammer's view of 8051
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 8-bit registers, these are DPH and DPLData RAM from location 08H to 7FHProgram memory from location 0000H to FFFFHProgram Counter (PC) of 16-bit
Read MoreRepresentation of fractions
To represent fractions may be necessary quite often inside the computer. For example, it may be needed to represent inside a computer a value like +0.610 or -0.610. To represent signed fractions, it is necessary to assume the binary point just after the MSB in the bit sequence. Such numbers where the binary point is assumed to be at a fixed position in the bit sequence are called fixed-point numbers.Unsigned fractions will have the assumed binary point at the extreme left. SM, 1's complement, and 2's complement fractions will have this imaginary binary point just to the right of the ...
Read More2's complement fractions
As an example, the value of 1 001, if the interpretation is that it is a 2's complement fraction will be as follows -It is 1.001 assuming the binary point after the MS bit. As the MS bit is 1, it is a negative number. Then the remaining bits do not specify the magnitude directly. The 2's complement of 1 001 is 0110+ 1 = 0 111. This is a positive fraction with the value 1 × 2−1 +1 × 2−2 +1 × 2−3 = 0.5 + 0.25 + 0.125 = 0.875 decimal. Thus, -0.875 is the value of 1001.If ...
Read MoreInstruction set of 8051
The instructions of 8051 Microcontroller can be classified into five different groups. These groups are like belowData Transfer GroupArithmetic GroupLogical GroupProgram Branch GroupBit Processing GroupThis Bit-Processing group is also known as Boolean Variable Manipulation.Like 8085, some instruction has two operands. The first operand is the Destination, and the second operator is Source.In the following examples, you will get some notations. The notations are like −Rn = Any register from R0to R7 Ri = Either R0 or R1 d8 = Any 8-bit immediate data (00H to FFH) d16 = 16-bit immediate data a8 = 8-bit address bit = 8-bit address of ...
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