CMSC 311- Computer Organization
Fall 1995 - Assignment #7
Due (at the beginning of class) Thursday, November 16
- From Mano, problem 5-13.
- From Mano, problem 5-24.
- Assume that, in the basic Mano computer the PC contains the
value 10016 at the beginning of a fetch cycle. The AC contains
555516, and the register R contains a zero. Memory location 10016
contains the value 020016, and memory location 20016 contains
the value AAAA16.
- Show the contents (in hex) of the PC, AC, AR, IR, and R registers
at the completion of the fetch cycle.
- Is the indirect cycle entered after this fetch cycle? If so,
show the contents of each of the above registers at the completion
of the indirect cycle.
- Show the contents of the above registers at the completion
of the execute cycle. What instruction is being executed?
- An important feature of many computers is memory protection.
One way to achieve memory protection by limiting the range of
addresses that a program can access. In this problem you are to
modify the basic Mano computer to have two additional registers
(LOW and HIGH) and check that all memory references are within
the range between LOW and HIGH.
- Add two new instructions to the machine SLO (F020) which transfers
the contents of the AC to the LOW register, and SHI (F010) which
transfers the contents of the AC to the HIGH register. Show the
control functions and micro-operations specific to these instructions.
- Design hardware to check that AR is in range: LOW <= AR
<= HIGH. Your circuit should have three 16 bit inputs, and
a single output INVALID which is 1 if the value of AR is outside
the allowed range.
- Modify the instruction cycle to check if a referenced memory
location is valid. If the memory reference is out of range, the
hardware should trap (cause a subroutine call) to memory location
0002. Show the modified list of micro-operations for the fetch,
decode, and indirect steps. (You should not need to add additional
time steps to the sequence.) Model your implementation on the
interrupt code by adding a trap cycle. Show the micro-operations
for the trap cycle.
- From Mano, problem 6-14.