Marking of Mid-Term Exam
Question 1
One mark was assigned for each of the following:
- correct entity declaration syntax
- correct architecture declaration
- correct (local) signal declarations (2 marks)
- counter reset logic
- counter increment logic
- transmit signal generation logic
- transmit signal logic (output signal not read)
- depth capture on echo input
- clocking of registers (2 marks)
Question 2
One mark was assigned for each of the following:
- reading the right register (300H)
- looking at the right bit for the switch (AND with 80H)
- conditional branch if switch not set
- initialize a counter register/location to 15 or 30
- increment/decrement the count
- looking at the right bit for the clock (AND with 01H)
- conditional branch if clock is set/not set
- checking for switch on during the time delay
(or using a program structure that accomplishes this)
- writing the right register location (300H)
- writing the right bit in the output register (01H)
- branch to restart of code (rather than exiting)
Many students used AX to read the 1-byte register instead of AL.
Marks were not deducted for this.
Many students tried to use rotate or shift instructions to
isolate bits instead of using bit masks.
Using "tricks" such as this requires a detailed understanding of
the behaviour of a particular processor and should be avoided.
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