Found 409 Articles for Microcontroller

Now in this topic we assume that 8085 is the processor which is used in this microcomputer system. In this slave, no 8259 slaves are used. We should examine properly before 8259 PIC is used in the microcomputer system for performing the interrupt control application. 8259 is configured in such a fantastic way that is found that a variety of information are provided like for IR0 request IV, interrupts like level or edge-triggered, whether 8259s are used single or many, if ICW4 is in need or not and whether for the interrupt requests masking should be done or not. This ... Read More

It is also an 8-bit register. The processor here writes to SLR but cannot read. The content of this register here implies a different meaning for Master8259 and Slave 8259. Through Master 8259 information is carried through the IR inputs to which Slave 8259s are connected. If the SLR of Master 8259 is loaded with the value 00001111, then it signifies that:The Slave exists on 8259 namely called as IR0, IR1, IR2 and IR3.No Slave exists on 8259 on this registers IR4, IR5, IR6 and IR7.A Slave 8259 serves information about the IR input of Master 8259 to which the ... Read More

Also, an 8-bit register which keeps track records of the interrupt requests that are currently being executed. If the request IR6 is currently being served, whose contents of ISR will be 01000000. If by any means the request to IR3 becomes active during the service process of IR6, 8259 sets bit 3 of ISR to 1 and activates the output INT. But bit 6 of ISR always remains set at 1 asIR6 request which is not fully serviced. Hence the contents ofISR become 01001000. The following assumptions stated below helps this to happen.Until 8259 operates in a complete nested mode, without ... Read More

It stores the levels of interrupts to be masked by means of storing the bits of the interrupt level already masked. It differs from other registers by means of only masking of the bits. Other processes remained intact. Let’s take for the assumption that the requests to the IR4 AND IR6 should not be an interrupt to the processor which can be well achieved by setting the bits of IMR to 1. The IMR is written by OCW1 command. The processor here also has the capability to read the contents of the IMRregister. To complete this task, the processor has ... Read More

An 8-bit register in which the tracks of active interrupt requests are kept. Whenever activation of an interrupt request input is done the bit corresponding in IRR register is set to 1. For example, if we activate the IR4 and IR6 inputs bits no 4 and 6 of IRR are set to 1 by making the contents of IRR as 01010000. But the processor is designed only to read the contents of this register but cannot write it to IRR. To read the IRR contents, the processor only has an issue the OCW3 command to the 8259 along with the LS 3 ... Read More

The 8259 is a specialized I/O port chip. It is never used in the interfacing of I/O devices but is only used for controlling the interrupts in a microcomputer.8259 consists of A0 as the only address input pin. Hence for a microprocessor, only two addresses are possible for the 8259 ports. The two ports can be termed as low port and high port.The processor selects the low port when A0 = 0The processor selects the high port when A0 = 1The processor issues some words termed as command words to these ports so as to configure the 8259 better. There are ... Read More

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 More

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 More

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 More

8085 microprocessor, consists of five interrupt input pins named as RST 5.5, RST 6.5, RST7.5, INTR, and TRAP respectively. When there are a maximum of five I/O devices they want to perform driven interrupt data transfer, which is connected to the five interrupt input pins. Now considering the case where there are more than five I/O devices which would like to perform an interrupt driven data transfer scheme. Here for some pins termed as an interrupt, we use more than one I/O device to the process. Most of the microprocessors nowadays have the configuration of these interrupt input pins. There ... Read More