In the 8085, restart instruction RST n vectors to address 8×n. Therefore RST 5 vectors to 5×8=40 decimal = 28H.
Formula / Key Relation
Vector address of RST n = 8n
RST 5: 8×5=40₁₀=28H
Address = 0028H
Detailed Explanation
Concept & Reasoning
The 8085 reserves fixed restart locations separated by 8 bytes: RST0 at 0000H, RST1 at 0008H, …, RST5 at 0028H. This should not be confused with hardware interrupt vector addresses such as RST5.5, RST6.5 and RST7.5.
How to Solve It in the Exam
RST number × 8 → hexadecimal vector address.
Important Exam Point
Differentiate software RST 5 from hardware RST 5.5.
Related Revision Path
This question sits in the revision path Microprocessors and Interfacing → 8085 Microprocessor → Interrupts .
Quick Trick
RST number × 8 → hexadecimal vector address.
Common Mistake
Writing 0032H by treating decimal 40 as hexadecimal 40.
Exam Tip
Differentiate software RST 5 from hardware RST 5.5.
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