In 8085 microprocessor, the RST6.5 interrupt transfer programmer execution to following location.
A
0034h
B
0024h
C
0048h
D
0060h

Question

In 8085 microprocessor, the RST6.5 interrupt transfer programmer execution to following location.

Examoogle · Accepted Answer

0034h

Explanation: In the Intel 8085 microprocessor, the restart (RST) interrupts are vectored interrupts that jump to specific, predefined memory addresses. For the RST 6.5 interrupt, the processor automatically loads the program counter with the address 0034h.

Working Principle: The 8085 has five hardware interrupts: TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. The vectored address for any RST n.5 is calculated using the formula $Address = n 	imes 8$. For RST 6.5, $6.5 	imes 8 = 52$ in decimal, which is equal to $34$ in hexadecimal (0034h). Upon receiving a high signal on the RST 6.5 pin, the CPU completes the current instruction, pushes the Program Counter onto the stack, and branches to this fixed address.

Key Formulas: $Address = (n) 	imes 8$ — The general vectoring formula for RST interrupts, where $n$ is the interrupt level.

Key Points: RST 6.5 is a maskable, vectored hardware interrupt.; The priority of RST 6.5 is higher than RST 5.5 and INTR, but lower than TRAP and RST 7.5.; The vector address is always calculated in units of 8 bytes.

Advantages: Eliminates the need for polling peripheral devices.; Fast response time for critical hardware events.

Disadvantages: Fixed memory locations limit flexibility in complex operating systems.; Interrupts must be enabled using the EI instruction to be recognized.

Applications: Real-time data acquisition.; Peripheral status monitoring.; Time-critical task switching.

Additional Info: RST 7.5 jumps to 003Ch (7.5*8 = 60d = 3Ch).. RST 5.5 jumps to 002Ch (5.5*8 = 44d = 2Ch).. Option B (0024h) corresponds to TRAP or custom mapping, not RST 6.5.

Answer: A is correct — The RST 6.5 interrupt in an 8085 microprocessor is hardwired to jump to memory location 0034h.

Exam Tip: Remember that 8085 vectored addresses are always multiples of 8; if you forget the specific value, multiply the RST number by 8 and convert the decimal result to hex.

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