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Microcontroller Articles
Page 4 of 33
Overview of the working of 8259
The interrupt requests are accepted by 8259 from many interrupting devices IR0 to IR7 pins. After that, it identifies the highest priority interrupt request from those inputs that are already active. To configure the 8259 for fixed priority mode of operation, among them IR0 has the highest and IR7 has the lowest priority. If the inputs IR2, IR4, and IR6 are active, thenIR2 has the highest priority interrupt request among the active requests than the other. The details of the interrupt requests those are active are stored in the Interrupt Request Register (IRR).By loading the Interrupt Mask Register (IMR), it ...
Read MoreArchitecture of 8259
8259 Microprocessor is architected in a unique style. It can program by means of some interrupts conditions by means of level or interrupt level often called edge-triggered interrupt level. Masking is done to individual interrupt bits. As the number of 8259 increases interrupt pins up to 64 can be obtained. There are 3 registers 8259 contains along with one priority resolver(PR). They are as follows −Interrupt Request Register(IIR) − It stores the bits who requests the interrupt.Interrupt service register(ISR) − It stores the currently interrupt levels.Interrupt Mask Register(IMR) − Stores the interrupt levels to be masked.PriorityResolver(PR) − Set the priority of ...
Read MorePins of 8259
Intel 8259 is designed as a 28-pin-programmable IC available as a package named DIP (Dual inline package). Its physical and functional pin diagrams are indicated below.PIN NameDescription and PurposesVcc and GndIt is the Power supply and ground pins. +5V power supply isused in this chip.D7-0For communication with the processor, there are Eight bi-directional data pins.RD*It is active low-input pin activated by the processor to read the information status from the 8259.WR*It is an active low-input pin which is activated by the processor to write the control information to 8259.CS*For selecting the chip it is used an active low input pin.A0An ...
Read More8085 Program to Check the fourth bit of a byte
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 More8085 Program to Multiply two numbers of size 8 bits
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 MoreALE pin in 8085 Microprocessor
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 MoreIO/M* PIN in 8085 Microprocessor
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 MoreProgrammer's view of 8085 Microprocessor
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 MoreAccumulator 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 ...
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