Question is about Perform program fetch/execute cycles for the following initial memory and program states. Here are some notes/hints and clarifications for how to perform these hypothetical machine simulations by hand:
- When executing the machine instructions, if the PC ends up referencing a memory address that you were not given values for, then you are done. This means that for some of the questions you may only fill in the first 6 of the 8 cells. But for others, like if there is an infinite loop, if you fill up all 8 cells you don’t have to do any more work, you are done at that point.
- It is possible for one or more of the questions to end up with a negative number as your result in the accumulator. If you read our textbook, and look at the figure , there is a definition for our hypothetical machine of how integers are to be represented. This integer representation uses a simple sign bit for the most significant bit, and the sign bit should be 1 to indicate a negative integer number. If you get a negative number in your AC, make sure you correctly represent it using the defined integer representation format for our hypothetical machine. It should be displayed as a hexadecimal number in the answer you give for the problem set.
- All values given in the memory and registers for the problem are hexadecimal (base 16), that represent 16 bits of information. You should represent all results as hexadecimal values as well, including signed integers. So for example, you should not result -1 if your result is negative 1, but the signed integer representation of this value according to our hypothetical machine, 0x8001
- The jump if zero instruction performs a conditional jump depending on if the previous result (the value in the accumulator) was zero or nonzero. Only jump to the indicated address if the result was 0. Likewise the jump if negative instruction depends on the previous accumulator result, and the jump should occur only if the previous accumulator result was a negative number.
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