Microelectronics with questions and
well verified answers actual exam!!!
2026
Embedded System Definition - ANSWER -stand-alone electronic system, designed to
perform specific functions within a larger system. E.g: GPS in a car, Heating systems within a
car.
Why isn't a PC an embedded system - ANSWER -It performs multiple tasks at once.
ROM - ANSWER -stores the programme code permanently, retaining information even
when power is removed.
RAM - ANSWER -provides temporary storage for variables and data during operation,
enabling fast access for active processes.
Microcontroller Core Features - ANSWER -Clock Communicates to CPU to keep system
synchronized
Data Bus goes both ways
Address Bus connects from CPU to everything else.
Consists of:
ROM & RAM (Memory Architecture), I/O, Clock, CPU, and Instruction Decoder which decodes
instructions from data bus to CPU
Finding required resistance for LED using datasheet - ANSWER -Look at datasheet, find
where LED graph begins to curve up, note the voltage and corresponding current at this point,
calculate resistance using ohm's law:
(V_ref - V_led)/I_led.
,Here, V_ref is your switch on voltage (e.g. 3.3V)
LED example, say graph shows voltage at 2.2V and current is 5mA - ANSWER -Graph will
look something like this.
Thus, required resistance would be:
(3.3-2.2)/0.005 = 1.1/0.005
= 220 Ohms
Memory - ANSWER -Memory can be thought of as a stack, with each holding 32 bits and
located using an address, which is a serial number starting at 0. The address "points" to a
memory location.
Communication with memory - ANSWER -data is transferred between memory and
system via busses, these are shared sets of wires down which memory is transferred and join
the components. For the MCU, we have 32 bits and thus 32 wires (a wire per bit). So, EACH bus
has 32 parallel wires.
We also need control lines to synchronize timing, select read or write commands, and ensure
only one device uses the bus at a given time.
Von Neumann architecture - ANSWER -Here, the processor communicates directly to
the Memory Stack, using a data bus which goes both ways and an address bus which goes one
way, the control bus is mostly negligible
Harvard Architecture - ANSWER -This differs to Von Neumann, as it uses separate data
and address busses to communicate to ROM and RAM, making Von Neumann simpler and
cheaper, however Harvard is faster as you can access both memories at the same time.
# of addresses - ANSWER -Number of addresses is found by raising 2^(# of bits).
So, for our MCU, we have 2^32 addresses, which is 4,294,967,296 addresses.
Resolution calculation for DAC - ANSWER -DAC basically estimates a Analogue signal
using digital, like a bunch of really packed together square waves which look like a sine when
zoomed out. The higher the resolution the less square the wave appears, and thus the more
analogue it is.
, Resolution Calculation - ANSWER -To calculate resolution, take the v_ref divided by the
number of addresses. This finds what we need to split the voltage across to match the address
bits.
Resolution Example - ANSWER -2 bit DAC, with V_Ref = 1 Volt
Sol: 2^2 = 4 ---> 1/4 = 0.25 V. So, each jump is 0.25.
But, we start at 0 and have 4 jumps. So, max voltage is actually only 0.75V.
This will ALWAYS be the case, where max voltage = v_ref - resolution, as we are one jump
short of max voltage/v_ref.
Voltage out (DAC) - ANSWER -Voltage out can be found by taking the point in the
address (D, for digital value), then dividing that by the total number of address and multiplying
that ratio by v_ref.
So, V_o = D/(2^n) * V_ref
Example calculation - max V out for a 3 bit DAC with 3V reference - ANSWER -V_ref = 3V
n=3
V_o = ((2^n)-1)/2^3 * 3
V_o = 7/8 * 3
V_o = 2.625V,
or you can do 3/2^n and then do 3- 3/2^n
Kelvin Divider/Resistor Ladder - ANSWER -This is basically a large ladder of resistors
connect in series, thus current is all the same. We can use this as a primitive DAC, which filters
the circuit to a certain resolution based on how many resistors down the ladder we are. Really
hard to implement, as each bit needs a resistor. So, for 32 bit, we need like 4,294,967,296
resistors. pretty crazy
3 Bit DAC example - ANSWER -3 bit dac means we need 2^3 resistors, so 8 resistors. This
means our V_Ref will be I* 8R
Let's take V_out at the 4th step in the ladder. So, we get V = I*4R, as we have gone across 4
resistors of equal size R Ohms.
So, the V_out will be 1/2 V_ref, as we only have 4IR compared to V_ref's 8IR.
well verified answers actual exam!!!
2026
Embedded System Definition - ANSWER -stand-alone electronic system, designed to
perform specific functions within a larger system. E.g: GPS in a car, Heating systems within a
car.
Why isn't a PC an embedded system - ANSWER -It performs multiple tasks at once.
ROM - ANSWER -stores the programme code permanently, retaining information even
when power is removed.
RAM - ANSWER -provides temporary storage for variables and data during operation,
enabling fast access for active processes.
Microcontroller Core Features - ANSWER -Clock Communicates to CPU to keep system
synchronized
Data Bus goes both ways
Address Bus connects from CPU to everything else.
Consists of:
ROM & RAM (Memory Architecture), I/O, Clock, CPU, and Instruction Decoder which decodes
instructions from data bus to CPU
Finding required resistance for LED using datasheet - ANSWER -Look at datasheet, find
where LED graph begins to curve up, note the voltage and corresponding current at this point,
calculate resistance using ohm's law:
(V_ref - V_led)/I_led.
,Here, V_ref is your switch on voltage (e.g. 3.3V)
LED example, say graph shows voltage at 2.2V and current is 5mA - ANSWER -Graph will
look something like this.
Thus, required resistance would be:
(3.3-2.2)/0.005 = 1.1/0.005
= 220 Ohms
Memory - ANSWER -Memory can be thought of as a stack, with each holding 32 bits and
located using an address, which is a serial number starting at 0. The address "points" to a
memory location.
Communication with memory - ANSWER -data is transferred between memory and
system via busses, these are shared sets of wires down which memory is transferred and join
the components. For the MCU, we have 32 bits and thus 32 wires (a wire per bit). So, EACH bus
has 32 parallel wires.
We also need control lines to synchronize timing, select read or write commands, and ensure
only one device uses the bus at a given time.
Von Neumann architecture - ANSWER -Here, the processor communicates directly to
the Memory Stack, using a data bus which goes both ways and an address bus which goes one
way, the control bus is mostly negligible
Harvard Architecture - ANSWER -This differs to Von Neumann, as it uses separate data
and address busses to communicate to ROM and RAM, making Von Neumann simpler and
cheaper, however Harvard is faster as you can access both memories at the same time.
# of addresses - ANSWER -Number of addresses is found by raising 2^(# of bits).
So, for our MCU, we have 2^32 addresses, which is 4,294,967,296 addresses.
Resolution calculation for DAC - ANSWER -DAC basically estimates a Analogue signal
using digital, like a bunch of really packed together square waves which look like a sine when
zoomed out. The higher the resolution the less square the wave appears, and thus the more
analogue it is.
, Resolution Calculation - ANSWER -To calculate resolution, take the v_ref divided by the
number of addresses. This finds what we need to split the voltage across to match the address
bits.
Resolution Example - ANSWER -2 bit DAC, with V_Ref = 1 Volt
Sol: 2^2 = 4 ---> 1/4 = 0.25 V. So, each jump is 0.25.
But, we start at 0 and have 4 jumps. So, max voltage is actually only 0.75V.
This will ALWAYS be the case, where max voltage = v_ref - resolution, as we are one jump
short of max voltage/v_ref.
Voltage out (DAC) - ANSWER -Voltage out can be found by taking the point in the
address (D, for digital value), then dividing that by the total number of address and multiplying
that ratio by v_ref.
So, V_o = D/(2^n) * V_ref
Example calculation - max V out for a 3 bit DAC with 3V reference - ANSWER -V_ref = 3V
n=3
V_o = ((2^n)-1)/2^3 * 3
V_o = 7/8 * 3
V_o = 2.625V,
or you can do 3/2^n and then do 3- 3/2^n
Kelvin Divider/Resistor Ladder - ANSWER -This is basically a large ladder of resistors
connect in series, thus current is all the same. We can use this as a primitive DAC, which filters
the circuit to a certain resolution based on how many resistors down the ladder we are. Really
hard to implement, as each bit needs a resistor. So, for 32 bit, we need like 4,294,967,296
resistors. pretty crazy
3 Bit DAC example - ANSWER -3 bit dac means we need 2^3 resistors, so 8 resistors. This
means our V_Ref will be I* 8R
Let's take V_out at the 4th step in the ladder. So, we get V = I*4R, as we have gone across 4
resistors of equal size R Ohms.
So, the V_out will be 1/2 V_ref, as we only have 4IR compared to V_ref's 8IR.
