EL21C Class Test #1-- 19^th October 2002 [1 hour]--Attempt ALL questions

1. How many bytes of memory does each instruction (below) occupy:

(a) MOV H,A

(b) MOV D,M

(c) JNZ 1234H

(d) LXI HL, 4321H

(e) XRA M [5]

2. List the Flags in the 8085 CPU . [3]

3. Indicate the contents of the Flags for the following instructions:

(a) F3H + 15H

(b) 00H + 00H

(c) 22H + 8EH [3]

4. Explain how the RST 7 instruction operates. [3]

5. List the hardware Interrupts on the 8085 CPU, in order of priority. [3]

6. Explain, using the SIM instruction, how you would enable RST 6.5 but

disable the others. [3]

7. List the contents of the A-register, after the RIM instruction is executed.

[Ignore the Most Significant Bit (msb)]. [3]

8. A CPU has 18-address pins. What is the last (highest) address

that may be generated (show decimal value) ? [1]

9. What 8085 instruction moves the lsb of register A into the Carry

Flag and the Carry Flag contents to the msb of register A ? [1]

10. If the clock frequency of a CPU is 3 GHz, how much time is required

to execute an instruction of 2 states ? [1]

11. If the contents of HL (1234H) register are PUSHed onto the Stack and the

SP register = 20FFH, show a diagram of the contents of the four

memory locations, 20FCH - 20FFH. [2]

12. Design a Port Address decoder for the 8085 CPU that generates

a unique pulse for the instruction, OUT 43H. [5]

13. List any TWO 8085 CPU instructions that do not destroy the contents

of the source or destination register/locations. [2]

[Bonus question:] In which Faculty is the subject of Electronics taught ? [1]

Maximum mark is 35.