Chapter 5 · Watch, then practise
Interrupt Operations
Follow a peripheral request through interrupt selection, service, and return. Distinguish processor interrupt pins from the registers in an external interrupt controller.
4 questions · 4 with related videos. Matches are based on playlist titles; broader background matches are labeled.
What to study
- Polling and interrupt-driven I/O
- Interrupt service routines and returning to the interrupted program
- 8085 interrupt inputs and interrupt acknowledgement
- 8259A request, mask and in-service registers
- Priority selection and cascading
Chapter playlists
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Notes
Interrupt driven IO in Hindi | COA | Computer Organization and Architecture Lectures
Last moment tuitions · 11:47
Choose a video · 2 lectures
Related interrupt-driven and programmed I/O lessons from the existing COA chapter playlist.
1. Polling or interrupts?
How does an interrupt change the way a processor services a peripheral?
Polling repeatedly checks device status. An interrupt lets the device request service while the processor runs other work. The processor transfers control to a service routine and later resumes the interrupted program.
8259 Programmable Interrupt Controller: Block Diagram and Working Explained
Engineering Funda · 17:25
Supplementary 8259 block-diagram lesson for the request, mask and in-service register roles.
2. Separate requests, masks and service state
An 8259A request is waiting but masked. Which registers describe these states?
The IRR records pending requests; the IMR controls masking; the ISR records requests being serviced. A pending bit does not mean its handler is running. Masking makes a request ineligible under the controller’s selection rules.
8259 Programmable Interrupt Controller: Block Diagram and Working Explained
Engineering Funda · 17:25 · Background lecture
8259 operation background; the processor-specific acknowledgement differences are set out in the answer.
3. Follow an interrupt acknowledgement
What does the 8259A supply when the processor acknowledges an interrupt?
It supplies vectoring information for the selected request. Its format depends on the configured processor mode. Do not assume the MCS-80/85 and 8086 acknowledgement sequences are identical.
8085 PIN DIAGRAM & DESCRIPTION
COMAT WORLD · 25:01
Choose a video · 2 lectures
Pairs the existing 8085 pin lesson with a DMA lesson whose title explicitly identifies HOLD and HLDA.
4. Recognize 8085 control signals
Name the five 8085 interrupt inputs. Are HOLD and HLDA also interrupt inputs?
The inputs are TRAP, RST 7.5, RST 6.5, RST 5.5 and INTR. HOLD requests the bus for DMA; HLDA acknowledges that bus request. INTA is the interrupt-acknowledge signal, not another interrupt request input.