DIG3601 Assessment 5 (Major Test 3) 2023
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Nov 24, 2024
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DIG3601
Assessment 5 (Major Test 3)
2023-10-20
UNIVERSITY OF SOUTH AFRICA
SCHOOL OF ENGINEERING
CONTINUOUS ASSESSMENT
(Assessment 5)
Major Test 3 2023
DIG3601
Digital Systems
Examiner:
S Motepe
Moderator: M Makwena
Total Marks: 49
Weight of Assessment: 35%
This paper consists of 2 pages including this ‘cover’ page.
Instructions:
YOUR SCRIPT MUST BE SAVED WITH STUDENT NO, SUBJECT CODE AND
UPLOADED ON ASSESSMENT PLATFORM.
Additional student instructions
1.
Students must upload their answer scripts in a single PDF file (answer scripts must
not be password protected or uploaded as “read only” files)
2.
NO emailed scripts will be accepted.
3.
Students are advised to preview submissions (answer scripts) to ensure legibility
and that the correct answer script file has been uploaded.
4.
Incorrect file format and uncollated answer scripts will not be considered.
5.
Incorrect answer scripts and/or submissions made on unofficial platforms will not
be marked and no opportunity will be granted for resubmission.
6.
Mark awarded for incomplete submission will be the student’s final mark. No
opportunity for resubmission will be granted.
7.
Mark awarded for illegible scanned submission will be the student’s final mark. No
opportunity for resubmission will be granted.
8.
Submissions will only be accepted from registered student accounts.
DIG3601
Assessment 5 (Major Test 3)
2023-10-20
Question 1
(20 Marks)
Answer the following statements with
True or False.
You don’t need to give details, just write
True or False.
1.1.
To convert from ASCII to BCD the value 30H is subtracted from the ASCII value and answer
of the subtract operation will be the corresponding BCD digit.
(2)
1.2.
Every one of the interrupts can be enabled individually by setting or clearing a bit in the
Special Function Registers PIE1 (8Ch) and PIE2 (8Dh).
(2)
1.3.
The PIC16F877A device provides fifteen different interrupt sources.
(2)
1.4.
After processing, the T0IE flag should not be cleared by the software.
(2)
1.5.
The switch on a keyboard, is in most cases, a normally open push to make switch.
(2)
1.6.
Input port pins do not need to be able to distinguish clearly between a “1” and a “0”,
especially if the signal makes a transition from one level to the other.
(2)
1.7.
The idea behind indirect address is to use one of the registers as a “pointer” to indicate
which address will be operated upon.
(2)
1.8.
Software timing delays are routines that are quite widely used in programming as it is
used in a variety of I/O interfacing tasks and general programming.
(2)
1.9.
If a branch operation has to take place, the program counter has to be reloaded with the
address of the last instruction in the branch.
(2)
1.10.
With a pipeline the CPU can fetch an instruction from the memory and while that
instruction is being decoded and executed, the next instruction is fetched and held in the
pipeline, ready to be decoded next.
Question 2
(29 Marks)
1.
When are interrupts particularly useful?
(2)
2.
Each of the interrupt sources in a PIC16F877A are individually maskable. What does this
mean?
(2)
3.
What is a global interrupt enable bit provided for?
(2)
4.
When is the Timer0 interrupt flag activated?
(2)
5.
The interrupt flags are sampled during every machine cycle. If an interrupt is detected, there
is a sequence of events that will take place within the microprocessor
. State the first five
event in order/sequence of events.
(10)
6.
In PIC microcontrollers, explain what happens in pipelining when the program flow is altered?
(2)
7.
Draw a fully labelled logic diagram for interrupt sources.
(9.5)
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