What is Daisy Chain Priority Interrupt: to search out the priority of devices that send the interrupt request, we have a tendency to adopt this technique. The daisy chaining technique of building priority consists of a serial association of all devices that request an interrupt. The device with the very best priority is placed within the initial position, followed by lower priority devices up to the device with the bottom priority, that is placed last within the chain. What is Daisy Chain
The interrupt request line is common to all or any devices and forms a wired logic association. If any device has its interrupt signal within the low level state, the interrupt line goes to the low level state and allows the interrupt input within the CPU. When no interrupts are pending, the interrupt line stays within the high level state and no interrupts are recognized by the CPU. this can be like negative OR operation. The CPU responds to an interrupt request by enabling the interrupt acknowledge line. This signal is received by device one at its PI (priority in) input. The acknowledge signal passes on to following device through the PO (priority out) output on condition that device one isn’t requesting an interrupt. If device one has pending interrupt, it blocks the acknowledge signal from following device by putting zero within the PO output. It then proceeds to insert its own interrupt vector address (VAD) into the information bus for the CPU to use throughout the interrupt cycle. What is Daisy Chain
Which device sends the request to the CPU, can accepts the acknowledgement from the CPU which device won’t send that acknowledgement signal to following device. This procedure is outlined as below.
A device with a zero in its PI input generates a zero in its PO output to tell the next-lower-priority device that the acknowledge signal has been blocked. a tool that’s requesting an interrupt and contains a one in its PI input can intercept the acknowledge signal by putting a zero in its PO output. If the device doesn’t have pending interrupts, it transmits the acknowledgement signal to following device by putting a one in its PO output. So the device with PI=1 and PO=0 is that the one with the very best priority that’s requesting an interrupt, and this device places its VAD on the information bus. The daisy chain arrangement offers the very best priority to the device that receives the interrupt acknowledge signal from the CPU. The farther the device is from the primary position; the lower is its priority. Know more about What is Daisy Chain